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BackupPC(1) BackupPC user guide BackupPC(1)

BackupPC Introduction
This documentation describes BackupPC version 4.4.0, released on 20 Jun
2020.

Overview
BackupPC is a high-performance, enterprise-grade system for backing up
Unix, Linux, WinXX, and MacOSX PCs, desktops and laptops to a server's
disk. BackupPC is highly configurable and easy to install and maintain.

Given the ever decreasing cost of disks and raid systems, it is now practi-
cal and cost effective to backup a large number of machines onto a server's
local disk or network storage. For some sites this might be the complete
backup solution. For other sites additional permanent archives could be
created by periodically backing up the server to tape.

Features include:

* A clever pooling scheme minimizes disk storage and disk I/O. Identical
files across multiple backups of the same or different PC are stored
only once, resulting in substantial savings in disk storage and disk
writes.

* Compression provides additional reductions in storage, depending on the
type of data being backed up. The CPU impact of compression is low
since only new files (those not already in the pool) need to be com-
pressed.

* A powerful http/cgi user interface allows administrators to view the
current status, edit configuration, add/delete hosts, view log files,
and allows users to initiate and cancel backups and browse and restore
files from backups.

* The http/cgi user interface has internationalization (i18n) support,
currently providing English, French, German, Spanish, Italian, Dutch,
Polish, Portuguese-Brazilian, Chinese, Polish, Czech, Japanese, Ukrain-
ian, and Russian.

* No client-side software is needed. On WinXX the standard smb protocol
is used to extract backup data. On linux, unix or MacOSX clients,
rsync, tar (over ssh/rsh/nfs) or ftp is used to extract backup data.
Alternatively, rsync can also be used on WinXX (using cygwin), since
rsync provides for efficient transfers and allows incremental backups
to detect almost all changes.

* Flexible restore options. Single files can be downloaded from any
backup directly from the CGI interface. Zip or Tar archives for se-
lected files or directories from any backup can also be downloaded from
the CGI interface. Finally, direct restore to the client machine (us-
ing smb or tar) for selected files or directories is also supported
from the CGI interface.

* BackupPC supports mobile environments where laptops are only intermit-
tently connected to the network and have dynamic IP addresses (DHCP).
Configuration settings allow machines connected via slower WAN connec-
tions (eg: dial up, DSL, cable) to not be backed up, even if they use
the same fixed or dynamic IP address as when they are connected di-
rectly to the LAN.

* Flexible configuration parameters allow multiple backups to be per-
formed in parallel, specification of which shares to backup, which di-
rectories to backup or not backup, various schedules for full and in-
cremental backups, schedules for email reminders to users and so on.
Configuration parameters can be set system-wide or also on a per-PC ba-
sis.

* Users are sent periodic email reminders if their PC has not recently
been backed up. Email content, timing and policies are configurable.

* BackupPC is Open Source software hosted by GitHub.

BackupPC 4.0
This is the first release of 4.0, which is a significant rewrite of Back-
upPC. This section provides a short overview of the changes and features
in 4.0.

Here's a short summary of what has changed in V4:

* No use of hardlinks (except temporarily to do atomic renames). Refer-
ence counting is handled at the application level in a batch manner
(hardlinks will still remain for any legacy V3 backups).

* Backups are stored as "reverse deltas" - the most recent backup is al-
ways filled and older backups are reconstituted by merging all the
deltas starting with the nearest future filled backup and working back-
wards.

This is the opposite of V3 where incrementals are stored as "forward
deltas" to a prior backup (typically the last full backup or prior
lower-level incremental backup, or the last full in the case of rsync).

* Since the most recent backup is filled, viewing/restoring that backup
(which is the most common backup used) doesn't require merging any
deltas from other backups.

* The concepts of incr/full backups and unfilled/filled storage are de-
coupled. The most recent backup is always filled. By default, for the
remaining backups, full backups are filled and incremental backups are
unfilled, but that is configurable.

* Uses full-file MD5 digests, which are stored in the directory attrib
files. Each backup directory only contains an empty attrib file whose
name includes its own MD5 digest, which is used to look up the attrib
file's contents in the pool. In turn, that file contains the metadata
for every file in that directory, including each files's MD5 digest.

* The Pool layout still supports chains to handle md5 collisions. While
collisions can be constructed and are now well-known, they are highly
unlikely in the wild. Pool files are never renamed or moved, unlike
V3.

* Any backup can be deleted (deltas are merged into next older backup if
it is not filled).

* The reverse deltas allow "infinite incrementals" - no need for a full
backup if you are willing to trade speed for the risk that a file
change will not be detected if the metadata (eg, mtime or size) doesn't
change.

* An rsync "full" backup now uses --checksum (instead of --ignore-times),
which is much more efficient on the server side - the server just needs
to check the full-file checksum computed by the client, together with
the mtime, nlinks, size attributes, to see if the file has changed. If
you want a more conservative approach, you can change it back to --ig-
nore-times, which requires the server to send block checksums to the
client.

* The use of rsync --checksum allows BackupPC to guess a potential match
anywhere in the pool, even on a first-time backup. In that case, the
usual rsync block checksums are still exchanged to make sure the com-
plete file is identical.

* Uses a modified rsync called rsync_bpc (currently based on rsync-3.0.9)
on the server side (in place of File::RsyncP), with a C code interface
to the BackupPC storage. So the whole data path for rsync is now in
compiled C code, which is much faster than perl.

* Due to the use of rsync-3.X, acls and xattrs are supported, and many
other useful options (but not all) are supported. Rsync protocol 30
supports the efficient incremental file list, which significantly im-
proves memory usage and startup time. It also supports MD5 full-file
checksums, which match BackupPC's new digest. That allows a full-file
digest to be checked as easily as an mtime on the server side.

* Significant portions of the BackupPC code are now compiled C code in a
new module called BackupPC::XS that is dynamically linked to perl.

Here is a more detailed discussion:

* Completely new backup storage. No hardlinks! Backups are stored as
reverse deltas, with the most recent backup always filled. Prior
backup "n" contains the changes relative to prior backup "n+1".

* Since every backup is based on the last filled backup, the concept of
incremental levels is removed.

* Example: let's assume backup #4 is the most recent, and therefore
filled, and backups #0..3 are not filled.

Backups #0..3 store just the necessary reverse changes needed to recon-
struct those backups, relative to the next backup.

- To view/restore backup #4, all the information is stored in backup #4.
- To view/restore backup #3, backup #4 (the filled one), is merged with the deltas in #3.
- To view/restore backup #2, backup #4 (the filled one), is merged with the deltas in #3 and #2
- etc.

When a new backup is started (#5), we begin by renaming backup #4 to
#5. At that instant, backup #4 storage is now empty (which means back-
ups #4 and #5 are currently identical). As the backup runs, changes
are made to #5 with the changed/new files in place, and the opposite
changes are added to backup #4, to keep the "view" of backup #4 un-
changed.

After the backup is done, #5 is now the filled version of the latest
backup, and #4 contains the changes necessary to turn #5 back into the
state when backup #4 was done. If there are no changes detected in the
new backup, the storage tree for #4 will be empty. If just one file
changed, the new file will be below #5, and the prior file will be be-
low #4 (well, technically not quite true, since files aren't stored be-
low the backup trees; more correctly, the attrib file in #5 will point
to the new pool file, and the attrib file in #4 will point to the old
pool file).

* The concepts of incr/full backups and unfilled/filled storage are now
decoupled. The most recent backup is always filled (whether or not the
last backup was a full or incr). Certain older backups can be filled
for convenience to make restoring old backups faster (because fewer
backups need to be merged), and are used to specify expiry schedules.

* When a backup starts, there are several different cases that determine
how the backups are stored and whether prior deltas are stored:

1. No existing backups: create a new backup #0 and do a full backup in
place (ie: no prior deltas are stored).

2. V3 backups exist, but no V4 backups. The last V3 backup is dupli-
cated into V4 format, and a full backup is done in place (ie: no
prior deltas are stored).

3. Last V4 backup is a full, or more than $Conf{FillCycle} since last
filled backup. The last backup is duplicated to create a new
filled backup, and the new backup is done in place (ie: no prior
deltas are stored).

4. There are V4 backups and it's less than $Conf{FillCycle} since last
one is filled. Renumber the last backup to #n+1, and put the re-
verse deltas in initially empty backup tree #n.

5. CompressLevel has toggled on/off between backups. This isn't well
tested and it's very hard to support efficiently. We treat this as
a brand new (empty) backup in place, that is therefore filled.
That way we won't need to merge between backups with compress
on/off.

6. Last backup was a V4 partial. If prior V4 backup is filled (and
not partial), then just do another in-place backup. Otherwise,
treat as case 4. When complete (whether successful or another par-
tial), delete the prior deltas in #n, which merges the cumulative
changes into #n-1.

* The treatment of a "Partial" backup has changed. Unlike in V3 where
partials are removed prior to the next backup, in V4 partials are kept
and are used as the starting point for the next backup. See case 6
above. If the new backup fails, if no files have been backed up, the
empty backup #n is removed.

* Backups are stored as mangled directory trees, but each directory only
contains an "attrib" file. The attrib file is zero-length, and its
name includes the MD5 digest so the contents can be looked up in the
pool.

The attrib contents in the pool contains the directory contents: for
each file, that means the metadata, xattrs and the MD5 digest of the
file contents.

* A modified rsync called rsync_bpc, based on rsync 3.0.9, is used on the
server side, with a C code layer that emulates all the file-system OS
calls to be compatible with the BackupPC store. That means for rsync,
the data path is now fully in compiled C, which should mean a signifi-
cant speedup. It also means many (but not all) of the rsync options
are supported natively.

* Significant parts of the BackupPC storage and pooling code have been
written in C (the same code is used in the server rsync_bpc). Back-
upPC::FileZIO, BackupPC::PoolWrite, BackupPC::Attrib, BackupPC::Attrib-
Cache and BackupPC::PoolRefCnt (reference counting and storage) are all
replaced with BackupPC::XS, a C-code perl extension.

* Extended attributes (xattr) are supported. Rsync is configured to
"store acls using xattr", meaning both acls and xattrs are supported.

* infinite incrementals with rsync are supported. The most recent backup
is always filled, so an incremental will still leave the most recent
backup filled.

* any V4 backup can be deleted - dependencies are merged into the next
older backup if it isn't already filled.

* file digests are full-file MD5. Collisions are much more unlikely than
V3, but still possible. Duplicates are implemented with an extension
to the 16 byte MD5 digest (ie: 16 bytes for plain file, 17 bytes for
next 255 duplicates etc).

* V4 pool files are stored in a new hierarchy, two levels deep, with 7
bits at each level (ie: 128 directories at top-level, and each with 128
directories at next level).

* V4 pool files are never moved or renamed.

* Inodes for hardlinked files are stored in each backup tree. This makes
backing up hardlinks accurate, compared to V3, and provides for consis-
tent inode numbering across backups.

* zero-sized files or empty attribute files don't get written or pooled.

* the elimination of hardlinks means that reference counting has to be
maintained by the BackupPC code. This is one of the riskiest area in
terms of development and testing. Reference counts are maintained
per-backup, per-host, and for the whole pool.

Each operation that changes reference counts (eg: doing a new backup,
deleting a backup, or duplicating (filling) a backup) creates one or
more poolRefDelta files in that client's backup directory (ie:
TopDir/pc/HOST/NNN). These files are lists of MD5 digests, and corre-
sponding counts deltas.

Each night, BackupPC_nightly runs BackupPC_refCountUpdate, which, for
each host, updates the per-host reference count database with the new
deltas. It then combines all the per-host reference count files to
create the global pool reference count database.

BackupPC_refCountUpdate can run concurrently with backups. If you
still have V3 backups and pool, BackupPC_nightly still needs to run and
check for old V3 pool files that can be deleted. But since there are
no new V3 backups happening, BackupPC_nightly can run concurrently with
backups.

* There is a new utility BackupPC_fsck that can check/fix the per-host
and global reference counts. The per-host reference count database is
verified by parsing all the attrib files in each backup tree. The
global reference count database is verified by combing all the per-host
reference count databases and comparing them.

BackupPC_fsck cannot run when BackupPC is.

* When BackupPC_refCountUpdate updates the overall reference counts, it
removes pool files that have a reference count of zero. To avoid race
conditions, it uses a two-phase process. It first flags files that
have zero reference counts using one of the file attributes. The next
time it runs (typically 24 hours later), any flagged files that still
have zero reference count are then removed. The rest of the code knows
not to use flagged pool files to avoid race conditions.

* Progress indication: a simple status that shows the number of files
processed so far. It's hard to convert that to a percentage, since the
total isn't known until the end of the backup. But knowing the number
of files is quite helpful, since you can get an idea of the expected
total based on the prior backups, or knowing what configuration you
have changed (ie: adding a large new tree).

* BackupPC_link is removed since it is no longer used.

* Since files are no longer stored in backup trees, browsing the backup
trees is even harder than V3 (where you just had to deal with man-
gling). A new utility BackupPC_ls acts like "ls -l", showing accurate
directory listings of files, together with the MD5 digests.

BackupPC_ls can be given either an explicit hostname, number, and un-
mangled path, or can be given the full (mangled) path, which makes it
easier to use directory completion. It should be possible to configure
tcsh and bash, together with some new hooks in BackupPC_ls, to give a
more natural file/directory completion.

BackupPC_zcat also can take just the MD5 digest (which you can paste
from BackupPC_ls). Currently BackupPC_zcat doesn't support the tree
parsing that BackupPC_ls does (it can only zcat actual files), but
that should be easy to rectify.

* Configuration for expiry: since full/incr are decoupled from filled/un-
filled, expiry is a bit trickier.

The convention for expiry parameters is "FullKeepPeriod/FullKeepCnt"
etc refer to Filled backups, and "IncrKeepPeriod/IncrKeepCnt" refer to
Unfilled backups.

* V3 migration: nothing specific is needed. V4 can browse/view/restore
V3 backups. When you install V4, no changes are made to any V3 back-
ups. If you are upgrading from V3, be sure to set $Conf{PoolV3Enabled}
to 1 so the old V3 pool is searched for matching files.

* When you install V4, it will notice that the V3 pool exists. Run-
ning configure.pl should set $Conf{PoolV3Enabled} to 1 in that
case, but you should be sure to check that.

* When a V4 backup is first done, BackupPC_backupDuplicate is run to
duplicate the most recent V3 backup to create a new V4 backup. A
"filled" view of the most recent V3 backup is used to create a
"filled" V4 backup tree.

This step could be time consuming, since every file needs to be
read (as a V3 file) and written as a V4 file. However, the V4
pooling code knows about the V3 pool, so it will move the V3 pool
file into the V4 pool. So this duplication process doesn't burn a
lot of pool storage space, but every file still needs to be read
(to compute the MD5 digest) and "written" (really just match-
ing/linking).

* Expiry: all the V3 + V4 backups are considered on a combined basis
for expiry checking.

* On a clean new V4 install, the steps of computing and checking V3
digests is eliminated.

* Downgrading V4->V3: Not tested and not recommended. In theory you
can remove any new V4 backups, remove the V4 pool itself, and you
should be able to re-install V3 and still have access to your orig-
inal full working V3 store (except for any V3 backups that V4 might
have routinely removed based on normal backup expiry configura-
tion).

However, any V3 pool files moved to V4 will no longer be in the V3
pool. So subsequent V3 backups will burn more storage as files get
re-added to the old V3 pool.

Hopefully downgrading isn't necessary...

* Optimizations: the C code implementation should give a significant per-
formance advantage, as well as the more flexible.

Potential V4 optimizations that are planned, but not yet implemented,
include:

* rsync-bpc doesn't support checksum caching.

* rsync-bpc with --ignore-times actually reads each unchanged file
three times, and writes it once (normal rsync reads twice and
writes once; the extra one is due to compression). Some careful
optimization can eliminate two reads and the write. The final read
can be eliminated with checksum caching.

* BackupPC_refCountUpdate, BackupPC_fsck, BackupPC_backupDuplicate,
BackupPC_backupDelete are all single-threaded.

Backup basics
Full Backup
A full backup is a complete backup of a share. BackupPC can be config-
ured to do a full backup at a regular interval (typically weekly).
BackupPC can be configured to keep a certain number of full backups.
Exponential expiry is also supported, allowing full backups with vari-
ous vintages to be kept (for example, a settable number of most recent
weekly fulls, plus a settable number of older fulls that are 2, 4, 8,
or 16 weeks apart).

Incremental Backup
An incremental backup is a backup of files that have changed since the
last successful backup.

Rsync is the best option for BackupPC. Any files whose attributes have
changed (ie: uid, gid, mtime, modes, size) since the last full are
backed up. Deleted, new files and renamed files are detected by rsync
incrementals.

For SMB and tar, BackupPC uses the modification time (mtime) to deter-
mine which files have changed since the last backup. That means SMB
and tar incrementals are not able to detect deleted files, renamed
files or new files whose modification time is prior to the last
lower-level backup.

BackupPC can also be configured to keep a certain number of incremental
backups, and to keep a smaller number of very old incremental backups.

BackupPC "fills-in" incremental backups when browsing or restoring,
based on the levels of each backup, giving every backup a "full" ap-
pearance. This makes browsing and restoring backups much easier: you
can restore from any one backup independent of whether it was an incre-
mental or full.

Partial Backup
When a full or incremental backup fails or is canceled, the most recent
backup is labeled "partial". Prior to V4, that backup was incomplete,
and would be deleted when the next backup completed.

In V4 a partial backup denotes that the last backup is incomplete.
However, since V4 does backup updating in place, it represents the best
and latest backup. A partial backup can be browsed or used to restore
files just like a successful full or incremental backup. And it will
be used as the starting point for the next backup attempt.

Identical Files
BackupPC pools identical files. By "identical files" we mean files
with identical contents, not necessary the same permissions, ownership
or modification time. Two files might have different permissions, own-
ership, or modification time but will still be pooled whenever the con-
tents are identical. This is possible since BackupPC stores the file
metadata (permissions, ownership, and modification time) separately
from the file contents.

Prior to V4, identical files were stored using hardlinks. In V4+,
hardlinks are eliminated (except for temporary atomic renames), and
reference counting is done at the application level.

Backup Policy
Based on your site's requirements you need to decide what your backup
policy is. BackupPC is not designed to provide exact re-imaging of
failed disks. See "Some Limitations" for more information. However,
with rsync and tar transports for linux/unix clients, plus full support
for special file types, extended attributes etc, likely means an exact
image of a linux/unix file system can be made.

BackupPC saves backups onto disk. Because of pooling you can relatively
economically keep several weeks or months of old backups.

At some sites the disk-based backup will be adequate, without a sec-
ondary offsite cloud, disk or tape backup. This system is robust to any
single failure: if a client disk fails or loses files, the BackupPC
server can be used to restore files. If the server disk fails, BackupPC
can be restarted on a fresh file system, and create new backups from
the clients. The chance of the server disk failing can be made very
small by spending more money on increasingly better RAID systems. How-
ever, there is still the risk of catastrophic events like fires or
earthquakes that can destroy both the BackupPC server and the clients
it is backing up if they are physically nearby.

Some sites might choose to do periodic backups to tape or cd/dvd. This
backup can be done perhaps weekly using the archive function of Back-
upPC.

Other users have reported success with removable disks to rotate the
BackupPC data drives, or using rsync to mirror the BackupPC data pool
offsite.

In V4, since hardlinks are not used permanently, duplicating a V4 pool
is much easier, allowing remote copying of the pool.

Resources
BackupPC home page
The BackupPC project page is at:

https://backuppc.github.io/backuppc

This page has links to the current documentation, github project source
and general information.

Github
BackupPC development is hosted on github:

https://github.com/backuppc

Releases for BackupPC and the required packages BackupPC-XS and
rsync-bpc are available at:

https://github.com/backuppc/backuppc/releases
https://github.com/backuppc/backuppc-xs/releases
https://github.com/backuppc/rsync-bpc/releases

BackupPC Wiki
BackupPC has a Wiki at <https://github.com/backuppc/backuppc/wiki>.
Everyone is encouraged to contribute to the Wiki. Anyone with a Github
account can edit the Wiki.

Mailing lists
Three BackupPC mailing lists exist for announcements (backuppc-an-
nounce), developers (backuppc-devel), and a general user list for sup-
port, asking questions or any other topic relevant to BackupPC (back-
uppc-users).

The lists are archived on SourceForge:

https://sourceforge.net/p/backuppc/mailman/backuppc-users/

You can subscribe to these lists by visiting:

http://lists.sourceforge.net/lists/listinfo/backuppc-announce
http://lists.sourceforge.net/lists/listinfo/backuppc-users
http://lists.sourceforge.net/lists/listinfo/backuppc-devel

The backuppc-announce list is moderated and is used only for important
announcements (eg: new versions). It is low traffic. You only need to
subscribe to one of backuppc-announce and backuppc-users: back-
uppc-users also receives any messages on backuppc-announce.

The backuppc-devel list is only for developers who are working on Back-
upPC. Do not post questions or support requests there. But detailed
technical discussions should happen on this list.

To post a message to the backuppc-users list, send an email to

backuppc-users@lists.sourceforge.net

Do not send subscription requests to this address!

Other Programs of Interest
If you want to mirror linux or unix files or directories to a remote
server you should use rsync, <http://rsync.samba.org>. BackupPC uses
rsync as a transport mechanism; if you are already an rsync user you
can think of BackupPC as adding efficient storage (compression and
pooling) and a convenient user interface to rsync.

Two popular open source packages that do tape backup are Amanda
(<http://www.amanda.org>) and Bacula (<http://www.bacula.org>). These
packages can be used as complete solutions, or also as back ends to
BackupPC to backup the BackupPC server data to tape.

Avery Pennarun's bup (<https://github.com/bup/bup>) uses the git pack-
file format to do efficient incrementals and deduplication. Various
programs and scripts use rsync to provide hardlinked backups. See, for
example, Mike Rubel's site (<http://www.mikerubel.org/comput-
ers/rsync_snapshots>), JW Schultz's dirvish
(<http://www.dirvish.org/>), Ben Escoto's rdiff-backup
(<http://www.nongnu.org/rdiff-backup>), and John Bowman's rlbackup
(<http://www.math.ualberta.ca/imaging/rlbackup>).

BackupPC provides many additional features, such as compressed storage,
deduplicating any matching files (rather than just files with the same
name), and storing special files without root privileges. But these
other programs provide simple, effective and fast solutions and are
definitely worthy of consideration.

Road map
The new features planned for future releases of BackupPC are on the Wiki at
<https://github.com/backuppc/backuppc/wiki>.

Comments and suggestions are welcome.

You can help
BackupPC is free. I work on BackupPC because I enjoy doing it and I like to
contribute to the open source community.

BackupPC already has more than enough features for my own needs. The main
compensation for continuing to work on BackupPC is knowing that more and
more people find it useful. So feedback is certainly appreciated, both
positive and negative.

Also, everyone is encouraged to contribute patches, bug reports, feature
and design suggestions, new code, Wiki additions (you can do those di-
rectly) and documentation corrections or improvements. Answering questions
on the mailing list is a big help too.

Installing BackupPC
Requirements
BackupPC requires:

* A linux, solaris, or unix based server with a substantial amount of
free disk space (see the next section for what that means). The CPU and
disk performance on this server will determine how many simultaneous
backups you can run. You should be able to run 4-8 simultaneous backups
on a moderately configured server.

It is also recommended you consider either an LVM or RAID setup so that
you can expand the file system as necessary.

* Perl version 5.8.0 or later. If you don't have perl, please see
<http://www.cpan.org>.

* The perl modules BackupPC::XS (version >= 0.50) is required, and sev-
eral others, File::Listing, Archive::Zip, XML::RSS, JSON::XS, Net::FTP,
Net::FTP::RetrHandle, Net::FTP::AutoReconnect are recommended.

Try "perldoc BackupPC::XS" and "perldoc Archive::Zip" to see if you
have these modules. If not, fetch them from <http://www.cpan.org> and
see the instructions below for how to build and install them.

The CGI Perl module is required for the http/cgi user interface. CGI
was a core module, but from version 5.22 Perl no longer ships with it.

* If you are using rsync to backup linux/unix machines you should have
rsync on each client machine. Version 3+ is strongly recommended, but
earlier versions will work too. See <http://rsync.samba.org>. Use
"rsync --version" to check your version.

For BackupPC to use Rsync you will also need to install rsync-bpc on
the server.

* If you are using smb to backup WinXX machines you need smbclient and
nmblookup from the samba package. You will also need nmblookup if you
are backing up linux/unix DHCP machines. See <http://www.samba.org>.

See <http://www.samba.org> for source and binaries. It's pretty easy
to fetch and compile samba, and just grab smbclient and nmblookup,
without doing the installation. Alternatively, <http://www.samba.org>
has binary distributions for most platforms.

* If you are using tar to backup linux/unix machines, those machines
should have version 1.13.20 or higher recommended. Use "tar --version"
to check your version. Various GNU mirrors have the newest versions of
tar; see <http://www.gnu.org/software/tar/>.

* The Apache web server, see <http://www.apache.org>, preferably built
with mod_perl support.

* If rrdtool is installed on the BackupPC server, graphs of the pool us-
age will be maintained and displayed. To enable the graphs, point
$Conf{RrdToolPath} to the rrdtool executable.

What type of storage space do I need?
Starting with 4.0.0, BackupPC no longer uses hardlinks for storage of dedu-
plicated files. However, hardlinks are still used temporarily in a few
places for doing atomic renames, with a fallback doing a file copy if the
hardlink fails, and files are moved (renamed) across various paths that
turn into expensive file copies if they span multiple file systems.

So ideally BackupPC's data store (__TOPDIR__) is a single file system that
supports hardlinks. It is ok to use a single symbolic link at the
top-level directory (__TOPDIR__) to point the entire data store somewhere
else). You can of course use any kind of RAID system or logical volume
manager that combines the capacity of multiple disks into a single, larger,
file system. Such approaches have the advantage that the file system can be
expanded without having to copy it.

Any standard linux or unix file system supports hardlinks. NFS mounted
file systems work too (provided the underlying file system supports
hardlinks). But windows based FAT and NTFS file systems will not work.

In BackupPC 3.x, hardlinks are fundamental to deduplication, so a startup
check is done ensure that the file system can support hardlinks, since this
is a common area of configuration problems in v3. In 4.x, that check is
only done if the pool still contains v3 backups and pool files.

How much disk space do I need?
Here's one real example (circa 2002) for an environment that is backing up
65 laptops with compression off. Each full backup averages 3.2GB. Each in-
cremental backup averages about 0.2GB. Storing one full backup and two in-
cremental backups per laptop is around 240GB of raw data. But because of
the pooling of identical files, only 87GB is used. This is without com-
pression.

Another example, with compression on: backing up 95 laptops, where each
backup averages 3.6GB and each incremental averages about 0.3GB. Keeping
three weekly full backups, and six incrementals is around 1200GB of raw
data. Because of pooling and compression, only 150GB is needed.

Here's a rule of thumb. Add up the disk usage of all the machines you want
to backup (210GB in the first example above). This is a rough minimum space
estimate that should allow a couple of full backups and at least half a
dozen incremental backups per machine. If compression is on you can reduce
the storage requirements by maybe 30-40%. Add some margin in case you add
more machines or decide to keep more old backups.

Your actual mileage will depend upon the types of clients, operating sys-
tems and applications you have. The more uniform the clients and applica-
tions the bigger the benefit from pooling common files.

In addition to total disk space, you should make sure you have plenty of
inodes on your BackupPC data partition. Some users have reported running
out of inodes on their BackupPC data partition. So even if you have plenty
of disk space, BackupPC will report failures when the inodes are exhausted.
This is a particular problem with ext2/ext3 file systems that have a fixed
number of inodes when the file system is built. Use "df -i" to see your
inode usage.

Step 1: Getting BackupPC
Many linux distributions now include BackupPC, so installing BackupPC via
your package manager is the best approach.

For example, for Debian, supported by Ludovic Drolez, can be found at
<http://packages.debian.org/backuppc> and is included in the current stable
Debian release. On Debian, BackupPC can be installed with the command:

apt-get install backuppc

You should also install rsync-bpc; the BackupPC package might include it
already, but if not:

apt-get install rsync-bpc

If those commands work, you can skip to Step 3.

Alternatively, manually fetching and installing BackupPC is easy. Start by
downloading the latest version from

https://github.com/backuppc/backuppc/releases

Step 2: Installing the distribution
Note: most information in this step is only relevant if you build and in-
stall BackupPC yourself. If you use a package provided by a distribution,
the package management system should take of installing any needed depen-
dencies.

First off, there are several perl modules you should install. The first
one, BackupPC::XS, is required. The others are optional but highly recom-
mended. Use either your linux package manager, or the cpan command, or
follow the instructions in the README files to install these packages:

BackupPC::XS
Significant portions of BackupPC are implemented in C code contained in
this module. You can run "perldoc BackupPC::XS" to see if this module
is installed. You need to have version >= 0.50. BackupPC::XS is
available from:

https://github.com/backuppc/backuppc-xs/releases

and also CPAN.

Archive::Zip
To support restore via Zip archives you will need to install
Archive::Zip, also from <http://www.cpan.org>. You can run "perldoc
Archive::Zip" to see if this module is installed.

XML::RSS
To support the RSS feature you will need to install XML::RSS, also from
<http://www.cpan.org>. There is not need to install this module if you
don't plan on using RSS. You can run "perldoc XML::RSS" to see if this
module is installed.

JSON::XS
To support the JSON formated metrics you will need to install JSON::XS,
also from <http://www.cpan.org>. There is not need to install this mod-
ule if you don't plan on using JSON formated metrics. You can run
"perldoc JSON::XS" to see if this module is installed.

CGI The CGI Perl module is required for the http/cgi user interface. CGI
was a core module, but from version 5.22 Perl no longer ships with it
so you'll need to install it if you are using a recent version of perl.

SCGIThe SCGI Perl module is required to use the S/CGI protocol for the
http/cgi user interface.

File::Listing, Net::FTP, Net::FTP::RetrHandle, Net::FTP::AutoReconnect
To use ftp with BackupPC you will need four libraries, but actually
need to install only File::Listing from <http://www.cpan.org>. You can
run "perldoc File::Listing" to see if this module is installed.
Net::FTP is a standard module. Net::FTP::RetrHandle and Net::FTP::Au-
toReconnect included in BackupPC distribution.

To build and install these packages you should use the cpan command. At
the prompt, type

install BackupPC::XS

Alternatively, if you want to install these manually, you can fetch the
tarball from <http://www.cpan.org> and then run these commands:

tar zxvf BackupPC-XS-0.50.tar.gz
cd BackupPC-XS-0.50
perl Makefile.PL
make
make test
make install

The same sequence of commands can be used for each module.

Next, you should install rsync_bpc if you want to use rsync to backup
clients (which is the recommended approach for all client types). If you
don't use your package manager, fetch the release from:

https://github.com/backuppc/rsync-bpc/releases

Then run these commands (updating the version number as appropriate):

tar zxf rsync-bpc-3.0.9.5.tar.gz
cd rsync-bpc-3.0.9.5
./configure
make
make install

Now let's move onto BackupPC itself. After fetching BackupPC-4.4.0.tar.gz,
run these commands as root:

tar zxf BackupPC-4.4.0.tar.gz
cd BackupPC-4.4.0
perl configure.pl

The configure.pl script also accepts command-line options if you wish to
run it in a non-interactive manner. It has self-contained documentation
for all the command-line options, which you can read with perldoc:

perldoc configure.pl

Starting with BackupPC 3.0.0, the configure.pl script by default complies
with the file system hierarchy (FHS) conventions. The major difference
compared to earlier versions is that by default configuration files will be
stored in /etc/BackupPC rather than below the data directory,
__TOPDIR__/conf, and the log files will be stored in /var/log/BackupPC
rather than below the data directory, __TOPDIR__/log.

Note that distributions may choose to use different locations for BackupPC
files than these defaults.

If you are upgrading from an earlier version the configure.pl script will
keep the configuration files and log files in their original location.

When you run configure.pl you will be prompted for the full paths of vari-
ous executables, and you will be prompted for the following information.

BackupPC User
It is best if BackupPC runs as a special user, eg backuppc, that has
limited privileges. It is preferred that backuppc belongs to a system
administrator group so that sysadmin members can browse BackupPC files,
edit the configuration files and so on. Although configurable, the de-
fault settings leave group read permission on pool files, so make sure
the BackupPC user's group is chosen restrictively.

On this installation, this is __BACKUPPCUSER__.

For security purposes you might choose to configure the BackupPC user
with the shell set to /bin/false. Since you might need to run some
BackupPC programs as the BackupPC user for testing purposes, you can
use the -s option to su to explicitly run a shell, eg:

su -s /bin/bash __BACKUPPCUSER__

Depending upon your configuration you might also need the -l option.

If the -s option is not available on your operating system, you can
specify the -m option to use your login shell as invoked shell:

su -m __BACKUPPCUSER__

Data Directory
You need to decide where to put the data directory, below which all the
BackupPC data is stored. This needs to be a big file system.

On this installation, this is __TOPDIR__.

Install Directory
You should decide where the BackupPC scripts, libraries and documenta-
tion should be installed, eg: /usr/local/BackupPC.

On this installation, this is __INSTALLDIR__.

CGI bin Directory
You should decide where the BackupPC CGI script resides. This will
usually be below Apache's cgi-bin directory.

It is also possible to use a different directory and use Apache's
``<Directory>'' directive to specify that location. See the Apache
HTTP Server documentation for additional information.

On this installation, this is __CGIDIR__.

Apache image Directory
A directory where BackupPC's images are stored so that Apache can serve
them. You should ensure this directory is readable by Apache and cre-
ate a symlink to this directory from the BackupPC CGI bin Directory.

Config and Log Directories
In this installation the configuration and log directories are located
in the following locations:

__CONFDIR__/config.pl main config file
__CONFDIR__/hosts hosts file
__CONFDIR__/pc/HOST.pl per-pc config file
__LOGDIR__/BackupPC log files, pid, status

The configure.pl script doesn't prompt for these locations but they can
be set for new installations using command-line options.

Step 3: Setting up config.pl
After running configure.pl, browse through the config file,
__CONFDIR__/config.pl, and make sure all the default settings are correct.
In particular, you will need to decide whether to use smb, tar,or rsync or
ftp transport (or whether to set it on a per-PC basis) and set the relevant
parameters for that transport method. See the section "Step 5: Client
Setup" for more details.

Step 4: Setting up the hosts file
The file __CONFDIR__/hosts contains the list of clients to backup. Back-
upPC reads this file in three cases:

* Upon startup.

* When BackupPC is sent a HUP (-1) signal. Assuming you installed the
init.d script, you can also do this with "/etc/init.d/backuppc reload".

* When the modification time of the hosts file changes. BackupPC checks
the modification time once during each regular wakeup.

Whenever you change the hosts file (to add or remove a host) you can either
do a kill -HUP BackupPC_pid or simply wait until the next regular wakeup
period.

Each line in the hosts file contains three fields, separated by whitespace:

Host name
This is typically the hostname or NetBios name of the client machine
and should be in lowercase. The hostname can contain spaces (escape
with a backslash), but it is not recommended.

Please read the section "How BackupPC Finds Hosts".

In certain cases you might want several distinct clients to refer to
the same physical machine. For example, you might have a database you
want to backup, and you want to bracket the backup of the database with
shutdown/restart using $Conf{DumpPreUserCmd} and $Conf{DumpPostUser-
Cmd}. But you also want to backup the rest of the machine while the
database is still running. In the case you can specify two different
clients in the host file, using any mnemonic name (eg: myhost_mysql and
myhost), and use $Conf{ClientNameAlias} in myhost_mysql's config.pl to
specify the real hostname of the machine.

DHCP flag
Starting with v2.0.0 the way hosts are discovered has changed and now
in most cases you should specify 0 for the DHCP flag, even if the host
has a dynamically assigned IP address. Please read the section "How
BackupPC Finds Hosts" to understand whether you need to set the DHCP
flag.

You only need to set DHCP to 1 if your client machine doesn't respond
to the NetBios multicast request:

nmblookup myHost

but does respond to a request directed to its IP address:

nmblookup -A W.X.Y.Z

If you do set DHCP to 1 on any client you will need to specify the
range of DHCP addresses to search is specified in $Conf{DHCPAddress-
Ranges}.

Note also that the $Conf{ClientNameAlias} feature does not work for
clients with DHCP set to 1.

User name
This should be the unix login/email name of the user who "owns" or uses
this machine. This is the user who will be sent email about this ma-
chine, and this user will have permission to stop/start/browse/restore
backups for this host. Leave this blank if no specific person should
receive email or be allowed to stop/start/browse/restore backups for
this host. Administrators will still have full permissions.

More users
Additional usernames, separated by commas and with no whitespace, can
be specified. These users will also have full permission in the CGI
interface to stop/start/browse/restore backups for this host. These
users will not be sent email about this host.

The first non-comment line of the hosts file is special: it contains the
names of the columns and should not be edited.

Here's a simple example of a hosts file:

host dhcp user moreUsers
farside 0 craig jim,dave
larson 1 gary andy

Step 5: Client Setup
Four methods for getting backup data from a client are supported: smb, tar,
rsync and ftp. Smb or rsync are the preferred methods for WinXX clients
and rsync or tar are the preferred methods for linux/unix/MacOSX clients.

The transfer method is set using the $Conf{XferMethod} configuration set-
ting. If you have a mixed environment (ie: you will use smb for some
clients and tar for others), you will need to pick the most common choice
for $Conf{XferMethod} for the main config.pl file, and then override it in
the per-PC config file for those hosts that will use the other method. (Or
you could run two completely separate instances of BackupPC, with different
data directories, one for WinXX and the other for linux/unix, but then com-
mon files between the different machine types will duplicated.)

Here are some brief client setup notes:

WinXX
One setup for WinXX clients is to set $Conf{XferMethod} to "smb". Ac-
tually, rsyncd is the better method for WinXX if you are prepared to
run rsync/cygwin on your WinXX client.

If you want to use rsyncd for WinXX clients you can find a pre-packaged
exe installer on <https://github.com/backuppc/cygwin-rsyncd/releases>.
The package is called cygwin-rsync. It contains rsync.exe, template
setup files and the minimal set of cygwin libraries for everything to
run. The README file contains instructions for running rsync as a ser-
vice, so it starts automatically everytime you boot your machine. If
you use rsync to backup WinXX machines, be sure to set
$Conf{ClientCharset} correctly (eg: 'cp1252') so that the WinXX file-
name encoding is correctly converted to utf8.

Otherwise, to use SMB, you can either create shares for the data you
want to backup or your can use the existing C$ share. To create a new
share, open "My Computer", right click on the drive (eg: C), and select
"Sharing..." (or select "Properties" and select the "Sharing" tab). In
this dialog box you can enable sharing, select the share name and per-
missions.

All Windows NT based OS (NT, 2000, XP Pro), are configured by default
to share the entire C drive as C$. This is a special share used for
various administration functions, one of which is to grant access to
backup operators. All you need to do is create a new domain user,
specifically for backup. Then add the new backup user to the built in
"Backup Operators" group. You now have backup capability for any direc-
tory on any computer in the domain in one easy step. This avoids using
administrator accounts and only grants permission to do exactly what
you want for the given user, i.e.: backup. Also, for additional secu-
rity, you may wish to deny the ability for this user to logon to com-
puters in the default domain policy.

The relevant configuration settings are $Conf{SmbShareName}, $Conf{Smb-
ShareUserName}, $Conf{SmbSharePasswd}, $Conf{SmbClientPath}, $Conf{Smb-
ClientFullCmd}, $Conf{SmbClientIncrCmd} and $Conf{SmbClientRestoreCmd}.

BackupPC needs to know the smb share username and password for a client
machine that uses smb. The username is specified in $Conf{Smb-
ShareUserName}. There are four ways to tell BackupPC the smb share
password:

* As an environment variable BPC_SMB_PASSWD set before BackupPC
starts. If you start BackupPC manually the BPC_SMB_PASSWD variable
must be set manually first. For backward compatibility for v1.5.0
and prior, the environment variable PASSWD can be used if
BPC_SMB_PASSWD is not set. Warning: on some systems it is possible
to see environment variables of running processes.

* Alternatively the BPC_SMB_PASSWD setting can be included in
/etc/init.d/backuppc, in which case you must make sure this file is
not world (other) readable.

* As a configuration variable $Conf{SmbSharePasswd} in
__CONFDIR__/config.pl. If you put the password here you must make
sure this file is not world (other) readable.

* As a configuration variable $Conf{SmbSharePasswd} in the per-PC
configuration file (__CONFDIR__/pc/$host.pl or
__TOPDIR__/pc/$host/config.pl in non-FHS versions of BackupPC).
You will have to use this option if the smb share password is dif-
ferent for each host. If you put the password here you must make
sure this file is not world (other) readable.

Placement and protection of the smb share password is a significant se-
curity issue, so please double-check the file and directory permis-
sions. In a future version there might be support for encryption of
this password, but a private key will still have to be stored in a pro-
tected place. Suggestions are welcome.

As an alternative to setting $Conf{XferMethod} to "smb" (using smb-
client) for WinXX clients, you can use an smb network filesystem (eg:
ksmbfs or similar) on your linux/unix server to mount the share, and
then set $Conf{XferMethod} to "tar" (use tar on the network mounted
file system).

Also, to make sure that filenames with special characters are correctly
transferred by smbclient you should make sure that the smb.conf file
has (for samba 3.x):

[global]
unix charset = UTF8

UTF8 is the default setting, so if the parameter is missing then it is
ok. With this setting $Conf{ClientCharset} should be empty, since smb-
client has already converted the filenames to utf8.

Linux/Unix
The preferred setup for linux/unix clients is to set $Conf{XferMethod}
to "rsync", "rsyncd" or "tar".

You can use either rsync, smb, or tar for linux/unix machines. Smb re-
quires that the Samba server (smbd) be run to provide the shares. Since
the smb protocol can't represent special files like symbolic links and
fifos, tar and rsync are the better transport methods for linux/unix
machines. (In fact, by default samba makes symbolic links look like
the file or directory that they point to, so you could get an infinite
loop if a symbolic link points to the current or parent directory. If
you really need to use Samba shares for linux/unix backups you should
turn off the "follow symlinks" samba config setting. See the smb.conf
manual page.)

Important note: many linux systems use sparse files for /var/log/last-
log, and have large special files below /proc and /run. Make sure you
exclude those directories and files when you configure your client.

The requirements for each Xfer Method are:

rsync
To use rsync, you need rsync-bpc installed on the BackupPC server.

On the client, you should have at least rsync 3.x. Rsync is run on
the remote client via ssh.

The relevant configuration settings are $Conf{RsyncClientPath},
$Conf{RsyncSshArgs}, $Conf{RsyncShareName}, $Conf{RsyncArgs},
$Conf{RsyncArgsExtra}, $Conf{RsyncFullArgsExtra}, and $Conf{Rsyn-
cRestoreArgs}.

rsyncd
To use rsync, you need rsync-bpc installed on the BackupPC server.

On the client, you should have at least rsync 3.x. In this case the
rsync daemon should be running on the client machine and BackupPC
connects directly to it.

The relevant configuration settings are $Conf{RsyncBackupPCPath},
$Conf{RsyncdClientPort}, $Conf{RsyncdUserName}, $Conf{Rsyncd-
Passwd}, $Conf{RsyncShareName}, $Conf{RsyncArgs}, $Conf{RsyncArg-
sExtra}, and $Conf{RsyncRestoreArgs}. $Conf{RsyncShareName} is the
name of an rsync module (ie: the thing in square brackets in
rsyncd's conf file -- see rsyncd.conf), not a file system path.

Be aware that rsyncd will remove the leading '/' from path names in
symbolic links if you specify "use chroot = no" in the rsynd.conf
file. See the rsyncd.conf manual page for more information.

tar You must have GNU tar on the client machine. Use "tar --version"
or "gtar --version" to verify. The version should be at least
1.13.20. Tar is run on the client machine via rsh or ssh.

The relevant configuration settings are $Conf{TarClientPath},
$Conf{TarShareName}, $Conf{TarClientCmd}, $Conf{TarFullArgs},
$Conf{TarIncrArgs}, and $Conf{TarClientRestoreCmd}.

ftp FTP Xfer Method is supported in V4 but not recommended since it
only handles minimal metadata, it doesn't support hardlinks or spe-
cial files, and can only restore regular files (not symbolic links
etc).

You need to be running an ftp server on the client machine. The
relevant configuration settings are $Conf{FtpShareName}, $Conf{Ft-
pUserName}, $Conf{FtpPasswd}, $Conf{FtpBlockSize}, $Conf{FtpPort},
$Conf{FtpTimeout}, and $Conf{FtpFollowSymlinks}.

You need to set $Conf{ClientCharset} to the client's charset so that
filenames are correctly converted to utf8. Use "locale charmap" on the
client to see its charset. Note, however, that modern versions of smb-
client and rsync handle this conversion automatically, so in most cases
you won't need to set $Conf{ClientCharset}.

For linux/unix machines you should not backup "/proc". This directory
contains a variety of files that look like regular files but they are
special files that don't need to be backed up (eg: /proc/kcore is a
regular file that contains physical memory). See $Conf{BackupFilesEx-
clude}. It is safe to backup /dev since it contains mostly charac-
ter-special and block-special files, which are correctly handed by
BackupPC (eg: backing up /dev/hda5 just saves the block-special file
information, not the contents of the disk). Similarly, on many linux
systems, /var/log/lastlog is a sparse file, with a very large apparent
size, so you should exclude that too.

Alternatively, rather than backup all the file systems as a single
share ("/"), it is easier to restore a single file system if you backup
each file system separately. To do this you should list each file sys-
tem mount point in $Conf{TarShareName} or $Conf{RsyncShareName}, and
add the --one-file-system option to $Conf{TarClientCmd} or $Conf{Rsyn-
cArgs}. In this case there is no need to exclude /proc explicitly
since it looks like a different file system.

Ssh allows BackupPC to run as a privileged user on the client (eg:
root), since it needs sufficient permissions to read all the backup
files. Ssh is setup so that BackupPC on the server (an otherwise low
privileged user) can ssh as root on the client, without being prompted
for a password. However, directly enabled ssh root logins is not good
practice. A better approach is the ssh as a regular user, and then
configure sudo to allow just rsync to be executed.

There are two common versions of ssh: v1 and v2. Here are some instruc-
tions for one way to setup ssh. (Check which version of SSH you have
by typing "ssh" or "man ssh".)

MacOSX
In general this should be similar to Linux/Unix machines. In versions
10.4 and later, the native MacOSX tar works, and also supports resource
forks. xtar is another option, and rsync works too (although the Ma-
cOSX-supplied rsync has an extension for extended attributes that is
not compatible with standard rsync).

SSH Setup
SSH is a secure way to run tar or rsync on a backup client to extract
the data. SSH provides strong authentication and encryption of the
network data.

Note that if you run rsyncd (rsync daemon), ssh is not used. In this
case, rsyncd provides its own authentication, but there is no encryp-
tion of network data. If you want encryption of network data you can
use ssh to create a tunnel, or use a program like stunnel.

Setup instructions for ssh can be found on the Wiki at
<https://github.com/backuppc/backuppc/wiki>.

Clients that use DHCP
If a client machine uses DHCP BackupPC needs some way to find the IP
address given the hostname. One alternative is to set dhcp to 1 in the
hosts file, and BackupPC will search a pool of IP addresses looking for
hosts. More efficiently, it is better to set dhcp = 0 and provide a
mechanism for BackupPC to find the IP address given the hostname.

For WinXX machines BackupPC uses the NetBios name server to determine
the IP address given the hostname. For unix machines you can run nmbd
(the NetBios name server) from the Samba distribution so that the ma-
chine responds to a NetBios name request. See the manual page and Samba
documentation for more information.

Alternatively, you can set $Conf{NmbLookupFindHostCmd} to any command
that returns the IP address given the hostname.

Please read the section "How BackupPC Finds Hosts" for more details.

Step 6: Running BackupPC
The installation contains an init.d backuppc script that can be copied to
/etc/init.d so that BackupPC can auto-start on boot. See init.d/README for
further instructions.

BackupPC should be ready to start. If you installed the init.d script,
then you should be able to run BackupPC with:

/etc/init.d/backuppc start

(This script can also be invoked with "stop" to stop BackupPC and "reload"
to tell BackupPC to reload config.pl and the hosts file.)

Otherwise, just run

__INSTALLDIR__/bin/BackupPC -d

as user __BACKUPPCUSER__. The -d option tells BackupPC to run as a daemon
(ie: it does an additional fork).

Any immediate errors will be printed to stderr and BackupPC will quit.
Otherwise, look in __LOGDIR__/LOG and verify that BackupPC reports it has
started and all is ok.

Step 7: Talking to BackupPC
You should verify that BackupPC is running by using BackupPC_serverMesg.
This sends a message to BackupPC via the unix (or TCP) socket and prints
the response. Like all BackupPC programs, BackupPC_serverMesg should be
run as the BackupPC user (__BACKUPPCUSER__), so you should

su __BACKUPPCUSER__

before running BackupPC_serverMesg. If the BackupPC user is configured
with /bin/false as the shell, you can use the -s option to su to explicitly
run a shell, eg:

su -s /bin/bash __BACKUPPCUSER__

Depending upon your configuration you might also need the -l option.

If the -s option is not available on your operating system, you can specify
the -m option to use your login shell as invoked shell:

su -m __BACKUPPCUSER__

You can request status information and start and stop backups using this
interface. This socket interface is mainly provided for the CGI interface
(and some of the BackupPC subprograms use it too). But right now we just
want to make sure BackupPC is happy. Each of these commands should produce
some status output:

__INSTALLDIR__/bin/BackupPC_serverMesg status info
__INSTALLDIR__/bin/BackupPC_serverMesg status jobs
__INSTALLDIR__/bin/BackupPC_serverMesg status hosts

The output should be some hashes printed with Data::Dumper. If it looks
cryptic and confusing, and doesn't look like an error message, then all is
ok.

The hosts status should produce a list of every host you have listed in
__CONFDIR__/hosts as part of a big cryptic output line.

You can also request that all hosts be queued:

__INSTALLDIR__/bin/BackupPC_serverMesg backup all

At this point you should make sure the CGI interface works since it will be
much easier to see what is going on. We'll get to that shortly.

Step 8: Checking email delivery
The script BackupPC_sendEmail sends status and error emails to the adminis-
trator and users. It is usually run each night by BackupPC_nightly.

To verify that it can run sendmail and deliver email correctly you should
ask it to send a test email to you:

su __BACKUPPCUSER__
__INSTALLDIR__/bin/BackupPC_sendEmail -u MYNAME@MYDOMAIN.COM

BackupPC_sendEmail also takes a -c option that checks if BackupPC is run-
ning, and it sends an email to $Conf{EMailAdminUserName} if it is not.
That can be used as a keep-alive check by adding

__INSTALLDIR__/bin/BackupPC_sendEmail -c

to __BACKUPPCUSER__'s cron.

The -t option to BackupPC_sendEmail causes it to print the email message
instead of invoking sendmail to deliver the message.

Step 9: CGI interface
The CGI interface script, BackupPC_Admin, is a powerful and flexible way to
see and control what BackupPC is doing. It is written for an Apache
server. If you don't have Apache, see <http://www.apache.org>.

There are three options for setting up the CGI interface:

SCGINew to 4.x, SCGI uses the SCGI interface to Apache, which requires the
mod_scgi.so module to be installed and loaded by Apache. This allows
Apache to run as any unprivileged user. The actual SCGI server runs as
the as the BackupPC user (__BACKUPPCUSER__), and handles the requests
from Apache via a TCP socket.

mod_perl
Mod_perl required the mod_perl module to be loaded by Apache. This al-
lows BackupPC_Admin to be run from inside Apache. Unlike SCGI, using
mod_perl with BackupPC_Admin requires a dedicated Apache to be run as
the BackupPC user (__BACKUPPCUSER__). This is because BackupPC_Admin
needs permission to access various files in BackupPC's data directo-
ries.

standard
The standard mode, which is significantly slower than SCGI or mod_perl,
is where Apache runs BackupPC_Admin as a separate process for every re-
quest. This adds significant startup overhead for every request, and
also requires that BackupPC_Admin be run as setuid to the BackupPC user
(__BACKUPPCUSER__), if Apache isn't being run as that user. Setuid
scripts are discouraged, so the preference is to use SCGI or mod_perl.

Here are some specifics for each setup:

SCGI Setup
First you need to install mod_scgi. If you can't find a pre-built
package, the source is available at <http://python.ca/scgi>. The re-
lease has subdirectories for apache1 and apache2. Pick your matching
version (nowadays most likely apache2). You'll need apxs, the Apache
Extension Tool, installed to build from source. Once compiled, the
module mod_scgi.so should be installed via the Makefile.

To enable the SCGI server, set $Conf{SCGIServerPort} to an available
non-privileged TCP port number, eg: 10268. The matching port number
has to appear in the Apache configuration file. Typical Apache config-
uration entries will look like this:

LoadModule scgi_module modules/mod_scgi.so
SCGIMount /BackupPC_Admin 127.0.0.1:10268
<Location /BackupPC_Admin>
AuthUserFile /etc/httpd/conf/passwd
AuthType basic
AuthName "access"
require valid-user
</Location>

Or a typical Nginx configuration file:

server {
listen 80;
server_name yourBackupPCServerHost;

root /var/www/backuppc;

access_log /var/log/nginx/backuppc.access.log;
error_log /var/log/nginx/backuppc.error.log;

location /BackupPC_Admin {
auth_basic "BackupPC";
auth_basic_user_file conf.d/backuppc.users;

include scgi_params;
scgi_pass 127.0.0.1:10268;
scgi_param REMOTE_USER $remote_user;
scgi_param SCRIPT_NAME $document_uri;
}
}

This allows the SCGI interface to be accessed with a URL:

http://yourBackupPCServerHost/BackupPC_Admin

You can use a different path or name if you prefer a different URL.
Unlike traditional CGI, there is no need to specify a valid path to a
CGI script.

Important security warning!! The SCGIServerPort must not be accessible
by anyone untrusted. That means you can't allow untrusted users access
to the BackupPC server, and you should block the SCGIServerPort TCP
port on the BackupPC server. If you don't understand what that means,
or can't confirm you have configured SCGI securely, then don't enable
SCGI - use one of the following two methods!!

Mod_perl Setup
The advantage of the mod_perl setup is that no setuid script is needed
(like in the standard method below), and there is a significant perfor-
mance advantage. Not only does all the perl code need to be parsed
just once, the config.pl and hosts files, plus the connection to the
BackupPC server are cached between requests. The typical speedup is
around 10-15x.

To use mod_perl you need to run Apache as user __BACKUPPCUSER__. If
you need to run multiple Apaches for different services then you need
to create multiple top-level Apache directories, each with their own
config file. You can make copies of /etc/init.d/httpd and use the -d
option to httpd to point each http to a different top-level directory.
Or you can use the -f option to explicitly point to the config file.
Multiple Apache's will run on different Ports (eg: 80 is standard, 8080
is a typical alternative port accessed via http://yourhost.com:8080).

Inside BackupPC's Apache http.conf file you should check the settings
for ServerRoot, DocumentRoot, User, Group, and Port. See
<http://httpd.apache.org/docs/server-wide.html> for more details.

For mod_perl, BackupPC_Admin should not have setuid permission, so you
should turn it off:

chmod u-s __CGIDIR__/BackupPC_Admin

To tell Apache to use mod_perl to execute BackupPC_Admin, add this to
Apache's 1.x httpd.conf file:

<IfModule mod_perl.c>
PerlModule Apache::Registry
PerlTaintCheck On
<Location /cgi-bin/BackupPC/BackupPC_Admin> # <--- change path as needed
SetHandler perl-script
PerlHandler Apache::Registry
Options ExecCGI
PerlSendHeader On
</Location>
</IfModule>

Apache 2.0.44 with Perl 5.8.0 on RedHat 7.1, Don Silvia reports that
this works (with tweaks from Michael Tuzi):

LoadModule perl_module modules/mod_perl.so
PerlModule Apache2

<Directory /path/to/cgi/>
SetHandler perl-script
PerlResponseHandler ModPerl::Registry
PerlOptions +ParseHeaders
Options +ExecCGI
Order deny,allow
Deny from all
Allow from 192.168.0
AuthName "Backup Admin"
AuthType Basic
AuthUserFile /path/to/user_file
Require valid-user
</Directory>

There are other optimizations and options with mod_perl. For example,
you can tell mod_perl to preload various perl modules, which saves mem-
ory compared to loading separate copies in every Apache process after
they are forked. See Stas's definitive mod_perl guide at
<http://perl.apache.org/guide>.

Standard Setup
The CGI interface should have been installed by the configure.pl script
in __CGIDIR__/BackupPC_Admin. BackupPC_Admin should have been in-
stalled as setuid to the BackupPC user (__BACKUPPCUSER__), in addition
to user and group execute permission.

You should be very careful about permissions on BackupPC_Admin and the
directory __CGIDIR__: it is important that normal users cannot directly
execute or change BackupPC_Admin, otherwise they can access backup
files for any PC. You might need to change the group ownership of Back-
upPC_Admin to a group that Apache belongs to so that Apache can execute
it (don't add "other" execute permission!). The permissions should
look like this:

ls -l __CGIDIR__/BackupPC_Admin
-swxr-x--- 1 __BACKUPPCUSER__ web 82406 Jun 17 22:58 __CGIDIR__/BackupPC_Admin

The setuid script won't work unless perl on your machine was installed
with setuid emulation. This is likely the problem if you get an error
saying such as "Wrong user: my userid is 25, instead of 150", meaning
the script is running as the httpd user, not the BackupPC user. This
is because setuid scripts are disabled by the kernel in most flavors of
unix and linux.

To see if your perl has setuid emulation, see if there is a program
called sperl5.8.0 (or sperl5.8.2 etc, based on your perl version) in
the place where perl is installed. If you can't find this program, then
you have two options: rebuild and reinstall perl with the setuid emula-
tion turned on (answer "y" to the question "Do you want to do se-
tuid/setgid emulation?" when you run perl's configure script), or
switch to the mod_perl alternative for the CGI script (which doesn't
need setuid to work).

BackupPC_Admin requires that users are authenticated by Apache. Specifi-
cally, it expects that Apache sets the REMOTE_USER environment variable
when it runs. There are several ways to do this. One way is to create a
.htaccess file in the cgi-bin directory that looks like:

AuthGroupFile /etc/httpd/conf/group # <--- change path as needed
AuthUserFile /etc/http/conf/passwd # <--- change path as needed
AuthType basic
AuthName "access"
require valid-user

You will also need "AllowOverride Indexes AuthConfig" in the Apache
httpd.conf file to enable the .htaccess file. Alternatively, everything can
go in the Apache httpd.conf file inside a Location directive. The list of
users and password file above can be extracted from the NIS passwd file.

One alternative is to use LDAP. In Apache's http.conf add these lines:

LoadModule auth_ldap_module modules/auth_ldap.so
AddModule auth_ldap.c

# cgi-bin - auth via LDAP (for BackupPC)
<Location /cgi-bin/BackupPC/BackupPC_Admin> # <--- change path as needed
AuthType Basic
AuthName "BackupPC login"
# replace MYDOMAIN, PORT, ORG and CO as needed
AuthLDAPURL ldap://ldap.MYDOMAIN.com:PORT/o=ORG,c=CO?uid?sub?(objectClass=*)
require valid-user
</Location>

If you want to disable the user authentication you can set $Conf{CgiAdmi-
nUsers} to '*', which allows any user to have full access to all hosts and
backups. In this case the REMOTE_USER environment variable does not have
to be set by Apache.

Alternatively, you can force a particular username by getting Apache to set
REMOTE_USER, eg, to hard code the user to www you could add this to
Apache's httpd.conf:

Finally, you should also edit the config.pl file and adjust, as necessary,
the CGI-specific settings. They're near the end of the config file. In
particular, you should specify which users or groups have administrator
(privileged) access: see the config settings $Conf{CgiAdminUserGroup} and
$Conf{CgiAdminUsers}. Also, the configure.pl script placed various images
into $Conf{CgiImageDir} that BackupPC_Admin needs to serve up. You should
make sure that $Conf{CgiImageDirURL} is the correct URL for the image di-
rectory.

See the section "Fixing installation problems" for suggestions on debugging
the Apache authentication setup.

How BackupPC Finds Hosts
Starting with v2.0.0 the way hosts are discovered has changed. In most
cases you should specify 0 for the DHCP flag in the conf/hosts file, even
if the host has a dynamically assigned IP address.

BackupPC (starting with v2.0.0) looks up hosts with DHCP = 0 in this man-
ner:

* First DNS is used to lookup the IP address given the client's name us-
ing perl's gethostbyname() function. This should succeed for machines
that have fixed IP addresses that are known via DNS. You can manually
see whether a given host have a DNS entry according to perl's gethost-
byname function with this command:

perl -e 'print(gethostbyname("myhost") ? "ok\n" : "not found\n");'

* If gethostbyname() fails, BackupPC then attempts a NetBios multicast to
find the host. Provided your client machine is configured properly, it
should respond to this NetBios multicast request. Specifically, Back-
upPC runs a command of this form:

nmblookup myhost

If this fails you will see output like:

querying myhost on 10.10.255.255
name_query failed to find name myhost

If it is successful you will see output like:

querying myhost on 10.10.255.255
10.10.1.73 myhost<00>

Depending on your netmask you might need to specify the -B option to
nmblookup. For example:

nmblookup -B 10.10.1.255 myhost

If necessary, experiment with the nmblookup command which will return
the IP address of the client given its name. Then update $Conf{Nm-
bLookupFindHostCmd} with any necessary options to nmblookup.

For hosts that have the DHCP flag set to 1, these machines are discovered
as follows:

* A DHCP address pool ($Conf{DHCPAddressRanges}) needs to be specified.
BackupPC will check the NetBIOS name of each machine in the range using
a command of the form:

nmblookup -A W.X.Y.Z

where W.X.Y.Z is each candidate address from $Conf{DHCPAddressRanges}.
Any host that has a valid NetBIOS name returned by this command (ie:
matching an entry in the hosts file) will be backed up. You can modify
the specific nmblookup command if necessary via $Conf{NmbLookupCmd}.

* You only need to use this DHCP feature if your client machine doesn't
respond to the NetBios multicast request:

nmblookup myHost

but does respond to a request directed to its IP address:

nmblookup -A W.X.Y.Z

Other installation topics
Removing a client
If there is a machine that no longer needs to be backed up (eg: a re-
tired machine) you have two choices. First, you can keep the backups
accessible and browsable, but disable all new backups. Alternatively,
you can completely remove the client and all its backups.

To disable backups for a client $Conf{BackupsDisable} can be set to two
different values in that client's per-PC config.pl file:

1. Don't do any regular backups on this machine. Manually requested
backups (via the CGI interface) will still occur.

2. Don't do any backups on this machine. Manually requested backups
(via the CGI interface) will be ignored.

This will still allow the client's old backups to be browsable and re-
storable.

To completely remove a client and all its backups, you should remove
its entry in the conf/hosts file, and then delete the
__TOPDIR__/pc/$host directory. Whenever you change the hosts file, you
should send BackupPC a HUP (-1) signal so that it re-reads the hosts
file. If you don't do this, BackupPC will automatically re-read the
hosts file at the next regular wakeup.

Note that when you remove a client's backups you won't initially re-
cover much disk space. That's because the client's files are still in
the pool. Overnight, when BackupPC_nightly next runs, all the unused
pool files will be deleted and this will recover the disk space used by
the client's backups.

Copying the pool
If the pool disk requirements grow you might need to copy the entire
data directory to a new (bigger) file system. Hopefully you are lucky
enough to avoid this by having the data directory on a RAID file system
or LVM that allows the capacity to be grown in place by adding disks.

Backups prior to V4 make extensive use of hardlinks. So unless you
have a virgin V4 installation, your file system will contain large num-
bers of hardlinks. This makes it hard to copy.

Prior to V4 (or a V4 upgrade to a V3 installation), the backup data di-
rectories contain large numbers of hardlinks. If you try to copy the
pool the target directory will occupy a lot more space if the hardlinks
aren't re-established.

Unless you have a pure V4 installation, the best way to copy a pool
file system, if possible, is by copying the raw device at the block
level (eg: using dd). Application level programs that understand
hardlinks include the GNU cp program with the -a option and rsync -H.
However, the large number of hardlinks in the pool will make the memory
usage large and the copy very slow. Don't forget to stop BackupPC
while the copy runs.

If you have a pure V4 installation, copying the pool and PC backup di-
rectories should be quite easy. Rsync 3.x should work well.

Fixing installation problems
If you find a solution to your problem that could help other users please
add it to the Wiki at <https://github.com/backuppc/backuppc/wiki>.

Restore functions
BackupPC supports several different methods for restoring files. The most
convenient restore options are provided via the CGI interface. Alterna-
tively, backup files can be restored using manual commands.

CGI restore options
By selecting a host in the CGI interface, a list of all the backups for
that machine will be displayed. By selecting the backup number you can
navigate the shares and directory tree for that backup.

BackupPC's CGI interface automatically fills incremental backups with the
corresponding full backup, which means each backup has a filled appearance.
Therefore, there is no need to do multiple restores from the incremental
and full backups: BackupPC does all the hard work for you. You simply se-
lect the files and directories you want from the correct backup vintage in
one step.

You can download a single backup file at any time simply by selecting it.
Your browser should prompt you with the filename and ask you whether to
open the file or save it to disk.

Alternatively, you can select one or more files or directories in the cur-
rently selected directory and select "Restore selected files". (If you
need to restore selected files and directories from several different par-
ent directories you will need to do that in multiple steps.)

If you select all the files in a directory, BackupPC will replace the list
of files with the parent directory. You will be presented with a screen
that has three options:

Option 1: Direct Restore
With this option the selected files and directories are restored di-
rectly back onto the host, by default in their original location. Any
old files with the same name will be overwritten, so use caution. You
can optionally change the target hostname, target share name, and tar-
get path prefix for the restore, allowing you to restore the files to a
different location.

Once you select "Start Restore" you will be prompted one last time with
a summary of the exact source and target files and directories before
you commit. When you give the final go ahead the restore operation
will be queued like a normal backup job, meaning that it will be de-
ferred if there is a backup currently running for that host. When the
restore job is run, smbclient, tar, rsync or rsyncd is used (depending
upon $Conf{XferMethod}) to actually restore the files. Sorry, there is
currently no option to cancel a restore that has been started. Cur-
rently ftp restores are not fully implemented.

A record of the restore request, including the result and list of files
and directories, is kept. It can be browsed from the host's home page.
$Conf{RestoreInfoKeepCnt} specifies how many old restore status files
to keep.

Note that for direct restore to work, the $Conf{XferMethod} must be
able to write to the client. For example, that means an SMB share for
smbclient needs to be writable, and the rsyncd module needs "read only"
set to "false". This creates additional security risks. If you only
create read-only SMB shares (which is a good idea), then the direct re-
store will fail. You can disable the direct restore option by setting
$Conf{SmbClientRestoreCmd}, $Conf{TarClientRestoreCmd} and $Conf{Rsyn-
cRestoreArgs} to undef.

Option 2: Download Zip archive
With this option a zip file containing the selected files and directo-
ries is downloaded. The zip file can then be unpacked or individual
files extracted as necessary on the host machine. The compression level
can be specified. A value of 0 turns off compression.

When you select "Download Zip File" you should be prompted where to
save the restore.zip file.

BackupPC does not consider downloading a zip file as an actual restore
operation, so the details are not saved for later browsing as in the
first case. However, a mention that a zip file was downloaded by a
particular user, and a list of the files, does appear in BackupPC's log
file.

Option 3: Download Tar archive
This is identical to the previous option, except a tar file is down-
loaded rather than a zip file (and there is currently no compression
option).

Command-line restore options
Apart from the CGI interface, BackupPC allows you to restore files and di-
rectories from the command line. The following programs can be used:

BackupPC_zcat
For each filename argument it inflates (uncompresses) the file and
writes it to stdout. To use BackupPC_zcat you could give it the full
filename, eg:

__INSTALLDIR__/bin/BackupPC_zcat __TOPDIR__/pc/host/5/fc/fcraig/fexample.txt > example.txt

It's your responsibility to make sure the file is really compressed:
BackupPC_zcat doesn't check which backup the requested file is from.
BackupPC_zcat returns a nonzero status if it fails to uncompress a
file.

In V4, BackupPC_zcat can be invoked in several other ways:

BackupPC_zcat file...
BackupPC_zcat MD5_digest...
BackupPC_zcat $TopDir/pc/host/num/share/mangledPath...
BackupPC_zcat [-h host] [-n num] [-s share] clientPath...

For example, you can do this:

BackupPC_zcat d73955e08410dfc5ea8069b05d2f43b2

That digest can be pasted from the output of BackupPC_ls.

The last form uses unmangled paths, so you can do this:

BackupPC_zcat -h HOST -n 10 -s / /home/craig/file

You can also mix real paths with unmangled paths. Both of these ver-
sions work:

BackupPC_zcat /data/BackupPC/pc/HOST/10/fhome/fcraig/ffile
BackupPC_zcat /data/BackupPC/pc/HOST/10/home/craig/file

BackupPC_tarCreate
BackupPC_tarCreate creates a tar file for any files or directories in a
particular backup. Merging of incrementals is done automatically, so
you don't need to worry about whether certain files appear in the in-
cremental or full backup.

The usage is:

BackupPC_tarCreate [options] files/directories...
Required options:
-h host host from which the tar archive is created
-n dumpNum dump number from which the tar archive is created
A negative number means relative to the end (eg -1
means the most recent dump, -2 2nd most recent etc).
-s shareName share name from which the tar archive is created;
can be "*" to mean all shares.

Other options:
-t print summary totals
-r pathRemove path prefix that will be replaced with pathAdd
-p pathAdd new path prefix
-b BLOCKS BLOCKS x 512 bytes per record (default 20; same as tar)
-w writeBufSz write buffer size (default 1048576 = 1MB)
-e charset charset for encoding filenames (default: value of
$Conf{ClientCharset} when backup was done)
-l just print a file listing; don't generate an archive
-L just print a detailed file listing; don't generate an archive

The command-line files and directories are relative to the specified
shareName. The tar file is written to stdout.

The -h, -n and -s options specify which dump is used to generate the
tar archive. The -r and -p options can be used to relocate the paths
in the tar archive so extracted files can be placed in a location dif-
ferent from their original location.

BackupPC_zipCreate
BackupPC_zipCreate creates a zip file for any files or directories in a
particular backup. Merging of incrementals is done automatically, so
you don't need to worry about whether certain files appear in the in-
cremental or full backup.

The usage is:

BackupPC_zipCreate [options] files/directories...
Required options:
-h host host from which the zip archive is created
-n dumpNum dump number from which the tar archive is created
A negative number means relative to the end (eg -1
means the most recent dump, -2 2nd most recent etc).
-s shareName share name from which the zip archive is created

Other options:
-t print summary totals
-r pathRemove path prefix that will be replaced with pathAdd
-p pathAdd new path prefix
-c level compression level (default is 0, no compression)
-e charset charset for encoding filenames (default: utf8)

The command-line files and directories are relative to the specified
shareName. The zip file is written to stdout. The -h, -n and -s op-
tions specify which dump is used to generate the zip archive. The -r
and -p options can be used to relocate the paths in the zip archive so
extracted files can be placed in a location different from their origi-
nal location.

BackupPC_ls
In V3, a full (or filled) backup tree contains all the files, albeit
with "mangled" names, and the file contents are compressed. Some users
found it convenient to directly navigate a PC's backup tree to check
for files.

In V4 that is not possible, since only a single attrib file is stored
per directory in the PC backup tree, so the directory contents aren't
visible without looking in the attrib file.

A new utility BackupPC_ls (like "ls") can be used to view PC backup
trees. It shows file digests, which can be pasted to BackupPC_zcat if
you want to view the file contents. The arguments are similar to Back-
upPC_zcat. The usage is:

BackupPC_ls [-iR] [-h host] [-n bkupNum] [-s shareName] dirs/files...

The -i option will show inodes (inode number and number of links). The
-R option recurses into directories.

If you don't specify -h, -n and -s, then you can specify the real file
system path instead. For example, the following three commands are
equivalent:

BackupPC_ls -h HOST -n 10 -s cDrive /home/craig/file
BackupPC_ls /data/BackupPC/pc/HOST/10/fcDrive/fhome/fcraig/ffile
BackupPC_ls /data/BackupPC/pc/HOST/10/cDrive/home/craig/file

As you can see, the portion of the full path after the backup number
can be either mangled or not. Note that using the mangled form allows
directory-name completion via the shell, since those directories actu-
ally exist.

It would be great if someone would like to volunteer to add features to
BackupPC_ls to make file and directory completion work with unmangled
names via the shell. In tcsh you can specify a completion program to
run - BackupPC_ls could be given special arguments to spit out the po-
tential (unmangled) completions. I'm not sure how bash does this.

Each of these programs reside in __INSTALLDIR__/bin.

Archive functions
BackupPC supports archiving to removable media. For users that require off-
site backups, BackupPC can create archives that stream to tape devices, or
create files of specified sizes to fit onto cd or dvd media.

Each archive type is specified by a BackupPC host with its XferMethod set
to 'archive'. This allows for multiple configurations at sites where there
might be a combination of tape and cd/dvd backups being made.

BackupPC provides a menu that allows one or more hosts to be archived. The
most recent backup of each host is archived using BackupPC_tarCreate, and
the output is optionally compressed and split into fixed-sized files (eg:
650MB).

The archive for each host is done by default using __INSTALLDIR__/bin/Back-
upPC_archiveHost. This script can be copied and customized as needed.

Configuring an Archive Host
To create an Archive Host, add it to the hosts file just as any other host
and call it a name that best describes the type of archive, e.g. ArchiveDLT

To tell BackupPC that the Host is for Archives, create a config.pl file in
the Archive Hosts's pc directory, adding the following line:

$Conf{XferMethod} = 'archive';

To further customise the archive's parameters you can add the changed para-
meters in the host's config.pl file. The parameters are explained in the
config.pl file. Parameters may be fixed or the user can be allowed to
change them (eg: output device).

The per-host archive command is $Conf{ArchiveClientCmd}. By default this
invokes

__INSTALLDIR__/bin/BackupPC_archiveHost

which you can copy and customize as necessary.

Starting an Archive
In the web interface, click on the Archive Host you wish to use. You will
see a list of previous archives and a summary on each. By clicking the
"Start Archive" button you are presented with the list of hosts and the ap-
proximate backup size (note this is raw size, not projected compressed
size) Select the hosts you wish to archive and press the "Archive Selected
Hosts" button.

The next screen allows you to adjust the parameters for this archive run.
Press the "Start the Archive" to start archiving the selected hosts with
the parameters displayed.

Starting an Archive from the command line
The script BackupPC_archiveStart can be used to start an archive from the
command line (or cron etc). The usage is:

BackupPC_archiveStart archiveHost userName hosts...

This creates an archive of the most recent backup of each of the specified
hosts. The first two arguments are the archive host and the username mak-
ing the request.

Other Command Line Utilities
These utilities are automatically run by BackupPC when needed. You don't
need to manually run these utilities.

BackupPC_attribPrint
BackupPC_attribPrint prints the contents of an attrib file. Usage:

BackupPC_attribPrint attribPath
BackupPC_attribPrint inodePath/inodeNum

BackupPC_backupDelete
BackupPC_backupDelete deletes an entire backup, or a directory path
within a backup. Usage:

BackupPC_backupDelete -h host -n num [-p] [-l] [-r] [-s shareName [dirs...]]
Options:
-h host hostname
-n num backup number to delete
-s shareName don't delete the backup; delete just this share
(or only dirs below this share if specified)
-p don't print progress information
-l don't remove XferLOG files
-r do a ref count update (default: none)
If a shareName is specified, just that share (or share/dirs) are deleted.
The backup itself is not deleted, nor is the log file removed.

BackupPC_backupDuplicate
BackupPC_backupDuplicate duplicates the last backup, which is used to
create a filled backup copy, and also to convert a V3 backup to a new
V4 starting point. Usage:

BackupPC_backupDuplicate -h host [-p]
Options:
-h host hostname
-p don't print progress information

BackupPC_fixupBackupSummary
BackupPC_fixupBackupSummary is used to re-create the backups file for
all the hosts if it is damaged or deleted. Usage:

BackupPC_fixupBackupSummary [-l]
Options:
-l legacy mode: try to reconstruct backups from LOG
files for backups prior to BackupPC v3.0.

BackupPC_fsck
BackupPC_fsck can only be run manually, and only while BackupPC isn't
running. It updates the host reference counts, the overall pool refer-
ence counts and stats. Usage:

BackupPC_fsck [options]
Options:
-f force regeneration of per-host reference counts
-n don't remove zero count pool files - print only
-s recompute pool stats

BackupPC_migrateV3toV4
If you upgraded an existing 3.x installation, BackupPC 4.x is backward
compatible with 3.x backups: it can browse, view and restore files.
However, the existing 3.x backups will still use hardlinks for storage,
and until those 3.x backups eventually expire, hardlinks will still be
used for 3.x backups.

BackupPC_migrateV3toV4 is an optional utility that can migrate existing
3.x backups to 4.x stoage format, eliminating hardlinks. This allows
you to eliminate the old V3 pool and you can then set $Conf{PoolV3En-
abled} to 0.

BackupPC_migrateV3toV4 -a [-m] [-p] [-v]
BackupPC_migrateV3toV4 -h host [-n V3backupNum] [-m] [-p] [-v]
Options:
-a migrate all hosts and all backups
-h host migrate just a specific host
-n V3backupNum migrate specific host backup; does all V3 backups
for that host if not specified
-m don't migrate anything; just print what would be done
-p don't print progress information
-v verbose

The BackupPC server should not be running when you run BackupPC_mi-
grateV3toV4. It will check and exit if the BackupPC server is running.

If you want to test BackupPC_migrateV3toV4, a cautious approach is to
make backup copies of the V3 backups, allowing you to restore them if
there is any issue. For example, if exampleHost has three 3.x backups
numbered 5, 6, 7, you can use cp -prl (preserving hardlinks) to make
copies:

cd /data/BackupPC/pc/exampleHost
mv 5 5.orig ; cp -prl 5.orig 5
mv 6 6.orig ; cp -prl 6.orig 6
mv 7 7.orig ; cp -prl 7.orig 7
cp backups backups.save

BackupPC_migrateV3toV4 -h exampleHost -n 5
BackupPC_migrateV3toV4 -h exampleHost -n 6
BackupPC_migrateV3toV4 -h exampleHost -n 7

If you want to put things back the way they were:

rm -rf 5 ; mv 5.orig 5
rm -rf 6 ; mv 6.orig 6
rm -rf 7 ; mv 7.orig 7
# copy the [567] lines from backups.save into backups;
# only do "cp backups.save backups" if you are sure no
# new backups have been done

Two important things to note with BackupPC_migrateV3toV4. First, V4
storage does use more filesystem inodes than V3 (that's the small cost
of getting rid of hardlinks). In particular, each directory in a
backup tree uses two inodes in V4 (one for the directory, and one for
the (empty) attrib file), and only one inode in V3 (one for the direc-
tory, and the attrib and all other files are hardlinked to the pool).
So before you run BackupPC_migrateV3toV4, make sure you have enough in-
odes in __TOPDIR__; use df -i to make sure you are under 45% inode us-
age.

Secondly, if you run BackupPC_migrateV3toV4 on all your backups, the
old V3 pool should be empty, except for old-style attrib files, which
should all have only one link since no backups should reference them
any longer. Before you turn off the V3 pool by setting $Conf{PoolV3En-
abled} to 0, make sure BackupPC_nightly has run enough times (specifi-
cally, $Conf{PoolSizeNightlyUpdatePeriod} times) so that the V3 pool
can be emptied. You could do this manually, but only if you are very
careful to check that the remaining files only have one link.

BackupPC_poolCntPrint
BackupPC_poolCntPrint is used to print reference count information, ei-
ther per-backup, per-host or for the entire pool depending on the file
path you use.

If you provide a hex md5 digest, the entire pool count for that digest
is printed. Usage:

BackupPC_poolCntPrint [poolCntFilePath|hexDigest]...

BackupPC_refCountUpdate
BackupPC_refCountUpdate is used to either update the per-backup and
per-host reference counts, or the system-wide reference counts. It is
used by BackupPC_dump, BackupPC_nightly, BackupPC_backupDelete, Back-
upPC_backupDuplicate and BackupPC_fsck. Usage:

BackupPC_refCountUpdate -h HOST [-c] [-f] [-F] [-o N] [-p] [-v]
With no other args, updates count db on backups with poolCntDelta files
and computers the host's total reference counts. Also builds refCnt for
any >=4.0 backups without refCnts.
-f - do an fsck on this HOST, which involves a rebuild of the
last two backup refCnts. poolCntDelta files are ignored.
Also forces fsck if requested by needFsck flag files
in TopDir/pc/HOST/refCnt. Equivalent to -o 2.
-F - rebuild all the >=4.0 per-backup refCnt files for this
host. Equivalent to -o 3.
-c - compare current count db to new db before replacing
-o N - override $Conf{RefCntFsck}.
-p - don't show progress
-v - verbose
Notes: in case there are legacy (ie: <=4.0.0alpha3) unapplied poolCntDelta
files in TopDir/pc/HOST/refCnt then the -f flag is turned on.

BackupPC_refCountUpdate -m [-f] [-p] [-c] [-r N-M] [-s] [-v] [-P phase]
-m Updates main count db, based on each HOST
-f - do an fsck on all the hosts, ignoring poolCntDelta files,
and replacing each host's count db. Will wait for backups
to finish if any are running.
-F - rebuild all the >=4.0 per-backup refCnt files.
-p - don't show progress
-c - clean pool files
-r N-M - process a subset of the main count db, 0 <= N <= M <= 255
-s - prints stats
-v - verbose
-P phase Phase from 0..15 each time we run BackupPC_nightly. Used
to compute exact pool size for portions of the pool based
on the phase and $Conf{PoolSizeNightlyUpdatePeriod}.

Other CGI Functions
Configuration and Host Editor
The CGI interface has a complete configuration and host editor. Only the
administrator can edit the main configuration settings and hosts. The edit
links are in the left navigation bar.

When changes are made to any parameter a "Save" button appears at the top
of the page. If you are editing a text box you will need to click outside
of the text box to make the Save button appear. If you don't select Save
then the changes won't be saved.

The host-specific configuration can be edited from the host summary page
using the link in the left navigation bar. The administrator can edit any
of the host-specific configuration settings.

When editing the host-specific configuration, each parameter has an "over-
ride" setting that denotes the value is host-specific, meaning that it
overrides the setting in the main configuration. If you deselect "over-
ride" then the setting is removed from the host-specific configuration, and
the main configuration file is displayed.

User's can edit their host-specific configuration if enabled via
$Conf{CgiUserConfigEditEnable}. The specific subset of configuration set-
tings that a user can edit is specified with $Conf{CgiUserConfigEdit}. It
is recommended to make this list short as possible (you probably don't want
your users saving dozens of backups) and it is essential that they can't
edit any of the Cmd configuration settings, otherwise they can specify an
arbitrary command that will be executed as the BackupPC user.

Metrics
BackupPC supports a metrics endpoint that expose common information in a
digest format. Allowed metrics formats are "json" (default), "prometheus"
and "rss". Format should be specified using "format" query parameter, a URL
similar to this will provide metrics information:

http://localhost/cgi-bin/BackupPC/BackupPC_Admin?action=metrics
http://localhost/cgi-bin/BackupPC/BackupPC_Admin?action=metrics?format=json
http://localhost/cgi-bin/BackupPC/BackupPC_Admin?action=metrics?format=prometheus
http://localhost/cgi-bin/BackupPC/BackupPC_Admin?action=metrics?format=rss

JSON format requires the JSON::XS module to be installed. RSS format re-
quires the XML::RSS module to be installed.

This feature is experimental. The information included will probably
change.

RSS
The RSS feed has been merged in the metrics endpoint (see section above).
Please use the metrics endpoint to access the RSS feed, as the old endpoint
will be deprecated.

BackupPC supports a very basic RSS feed. Provided you have the XML::RSS
perl module installed, a URL similar to this will provide RSS information:

http://localhost/cgi-bin/BackupPC/BackupPC_Admin?action=rss

This feature is experimental. The information included will probably
change.

BackupPC Design
Some design issues
Pooling common files
To see if a file is already in the pool, an MD5 digest of the file con-
tents is used. This can't guarantee a file is identical: it just re-
duces the search to often a single file or handful of files.

Depending on the Xfer method and settings, a complete file comparison
is done to verify if two files are really the same.

Prior to V4, identical files on multiples backups are represented by
hard links. Hardlinks are used so that identical files all refer to
the same physical file on the server's disk. Also, hard links maintain
reference counts so that BackupPC knows when to delete unused files
from the pool.

In V4+, hardlinks are not used and reference counting is done at the
application level. It is done in a batch manner, which simplifies the
implementation.

For the computer-science majors among you, you can think of the pooling
system used by BackupPC as just a chained hash table stored on a (big)
file system.

The hashing function
In V4+, the file digest is the MD5 digest of the complete file. While
MD5 collisions are now well known, and can be easily constructed, in
real use collisions will be extremely unlikely.

Prior to V4, just a portion of all but the smallest files was used for
the digest. That decision was made long ago when CPUs were a lot
slower. For files less than 256K, the digest is the MD5 digest of the
file size and the full file. For files up to 1MB, the first and last
128K of the file, and for over 1MB, the first and eighth 128K chunks
are used, together with the file size.

Compression
BackupPC supports compression. It uses the deflate and inflate methods
in the Compress::Zlib module, which is based on the zlib compression
library (see <http://www.gzip.org/zlib/>).

The $Conf{CompressLevel} setting specifies the compression level to
use. Zero (0) means no compression. Compression levels can be from 1
(least cpu time, slightly worse compression) to 9 (most cpu time,
slightly better compression). The recommended value is 3. Changing it
to 5, for example, will take maybe 20% more cpu time and will get an-
other 2-3% additional compression. Diminishing returns set in above 5.
See the zlib documentation for more information about compression lev-
els.

BackupPC implements compression with minimal CPU load. Rather than com-
pressing every incoming backup file and then trying to match it against
the pool, BackupPC computes the MD5 digest based on the uncompressed
file, and matches against the candidate pool files by comparing each
uncompressed pool file against the incoming backup file. Since inflat-
ing a file takes roughly a factor of 10 less CPU time than deflating
there is a big saving in CPU time.

The combination of pooling common files and compression can yield a
factor of 8 or more overall saving in backup storage.

Note that you should not turn compression on and off are you have
started running BackupPC. It will result in double the storage needs,
since all the files will be stored in both the compressed and uncom-
pressed pools.

BackupPC operation
BackupPC reads the configuration information from __CONFDIR__/config.pl. It
then runs and manages all the backup activity. It maintains queues of pend-
ing backup requests, user backup requests and administrative commands.
Based on the configuration various requests will be executed simultane-
ously.

As specified by $Conf{WakeupSchedule}, BackupPC wakes up periodically to
queue backups on all the PCs. This is a four step process:

1. For each host and DHCP address backup requests are queued on the back-
ground command queue.

2. For each PC, BackupPC_dump is forked. Several of these may be run in
parallel, based on the configuration. First a ping is done to see if
the machine is alive. If this is a DHCP address, nmblookup is run to
get the netbios name, which is used as the hostname. If DNS lookup
fails, $Conf{NmbLookupFindHostCmd} is run to find the IP address from
the hostname. The file __TOPDIR__/pc/$host/backups is read to decide
whether a full or incremental backup needs to be run. If no backup is
scheduled, or the ping to $host fails, then BackupPC_dump exits.

The backup is done using the specified XferMethod. Either samba's smb-
client or tar over ssh/rsh/nfs piped into BackupPC_tarExtract, or rsync
over ssh/rsh is run, or rsyncd is connected to, with the incoming data
extracted to __TOPDIR__/pc/$host/new. The XferMethod output is put
into __TOPDIR__/pc/$host/XferLOG.

The letter in the XferLOG file shows the type of object, similar to the
first letter of the modes displayed by ls -l:

d -> directory
l -> symbolic link
b -> block special file
c -> character special file
p -> pipe file (fifo)
nothing -> regular file

The words mean:

create
new for this backup (ie: directory or file not in pool)

poolfound a match in the pool

samefile is identical to previous backup (contents were checksummed and
verified during full dump).

skipfile skipped in incremental because attributes are the same (only
displayed if $Conf{XferLogLevel} >= 2).

As BackupPC_tarExtract extracts the files from smbclient or tar, or as
rsync or ftp runs, it checks each file in the backup to see if it is
identical to an existing file from any previous backup of any PC. It
does this without needed to write the file to disk. If the file matches
an existing file, a hardlink is created to the existing file in the
pool. If the file does not match any existing files, the file is writ-
ten to disk and inserted into the pool.

BackupPC_tarExtract and rsync can handle arbitrarily large files and
multiple candidate matching files without needing to write the file to
disk in the case of a match. This significantly reduces disk writes
(and also reads, since the pool file comparison is done disk to memory,
rather than disk to disk).

Based on the configuration settings, BackupPC_dump checks each old
backup to see if any should be removed.

3. Once each night, BackupPC_nightly is run to complete some additional
administrative tasks, such as cleaning the pool. This involves remov-
ing any files in the pool that only have a single hard link (meaning no
backups are using that file).

If BackupPC_nightly takes too long to run, the settings $Conf{MaxBack-
upPCNightlyJobs} and $Conf{BackupPCNightlyPeriod} can be used to run
several BackupPC_nightly processes in parallel, and to split its job
over several nights.

BackupPC also listens for TCP connections on $Conf{ServerPort}, which is
used by the CGI script BackupPC_Admin for status reporting and user-initi-
ated backup or backup cancel requests.

Storage layout
BackupPC resides in several directories:

__INSTALLDIR__
Perl scripts comprising BackupPC reside in __INSTALLDIR__/bin, li-
braries are in __INSTALLDIR__/lib and documentation is in __IN-
STALLDIR__/doc.

__CGIDIR__
The CGI script BackupPC_Admin resides in this cgi binary directory.

__CONFDIR__
All the configuration information resides below __CONFDIR__. This di-
rectory contains:

The directory __CONFDIR__ contains:

config.pl
Configuration file. See "Configuration File" below for more de-
tails.

hosts
Hosts file, which lists all the PCs to backup.

pc The directory __CONFDIR__/pc contains per-client configuration
files that override settings in the main configuration file. Each
file is named __CONFDIR__/pc/HOST.pl, where HOST is the hostname.

In pre-FHS versions of BackupPC these files were located in
__TOPDIR__/pc/HOST/config.pl.

__LOGDIR__
The directory __LOGDIR__ (__TOPDIR__/log on pre-FHS versions of Back-
upPC) contains:

LOG Current (today's) log file output from BackupPC.

LOG.0 or LOG.0.z
Yesterday's log file output. Log files are aged daily and com-
pressed (if compression is enabled), and old LOG files are deleted.

status.pl
A summary of BackupPC's status written periodically by BackupPC so
that certain state information can be maintained if BackupPC is
restarted. Should not be edited.

UserEmailInfo.pl
A summary of what email was last sent to each user, and when the
last email was sent. Should not be edited.

__RUNDIR__
The directory __RUNDIR__ (__TOPDIR__/log on pre-FHS versions of Back-
upPC) contains:

BackupPC.pid
Contains BackupPC's process id.

BackupPC.sock
A unix domain socket for communicating to the BackupPC server.

__TOPDIR__
All of BackupPC's data (PC backup images, logs, configuration informa-
tion) is stored below this directory.

Below __TOPDIR__ are several directories:

__TOPDIR__/pool
All uncompressed files from PC backups are stored below
__TOPDIR__/pool. Each file's name is based on the MD5 hex digest
of the file contents.

For V4+, the digest is the MD5 digest of the full file contents
(the length is not used). For V4+ the pool files are stored in a 2
level tree, using 7 bits from the top of the first two bytes of the
digest. So there are 128 directories are each level, numbered
evenly in hex from 0x00, 0x02, to 0xfe.

For example, if a file has an MD5 digest of
123456789abcdef0123456789abcdef0, the uncompressed file is stored
in __TOPDIR__/pool/12/34/123456789abcdef0123456789abcdef0.

Duplicates digest are represented with one (or more) hex byte ex-
tensions. So three colliding files would be stored as

__TOPDIR__/pool/12/34/123456789abcdef0123456789abcdef0
__TOPDIR__/pool/12/34/123456789abcdef0123456789abcdef000
__TOPDIR__/pool/12/34/123456789abcdef0123456789abcdef001

The rest of this section describes the old pool layout. Note that
both V3 and V4 pools can exist together, since they use different
names for their directory trees.

As exampled earlier, prior to V4 the digest is computed as follows.
For files less than 256K, the file length and the entire file is
used. For files up to 1MB, the file length and the first and last
128K are used. Finally, for files longer than 1MB, the file length,
and the first and eighth 128K chunks for the file are used.

Both BackupPC_dump (actually, BackupPC_tarExtract or rsync_bpc) are
responsible for checking newly backed up files against the pool.
For each file, the MD5 digest is used to generate a filename in the
pool directory.

If the file exists in the pool, the contents are compared. If
there is no match, additional files in the chain are checked (if
any). (Actually, multiple candidate files are compared in paral-
lel.)

If $Conf{PoolV3Enabled} is set, then the V3 pool is checked if
there are no matches in the V4 pool. If a V3 file matches, it is
simply moved (renamed) the the V4 pool with it's new filename based
on the V4 digest. That still allows the V3 backups to be browsed
etc, since those backups are still based on hardlinks.

If the file contents exactly match, a reference count is incre-
mented. Otherwise, the file is added to the pool by using an
atomic link operation, followed by unlinking the temporary file.

One other issue: zero length files are not pooled, since there are
a lot of these files and on most file systems it doesn't save any
disk space to turn these files into hard links.

Prior to V4, each pool file is stored in a subdirectory X/Y/Z,
where X, Y, Z are the first 3 hex digits of the MD5 digest.

For example, if a file has an MD5 digest of
123456789abcdef0123456789abcdef0, the file is stored in
__TOPDIR__/pool/1/2/3/123456789abcdef0123456789abcdef0.

The MD5 digest might not be unique (especially since not all the
file's contents are used for files bigger than 256K). Different
files that have the same MD5 digest are stored with a trailing suf-
fix "_n" where n is an incrementing number starting at 0. So, for
example, if two additional files were identical to the first, ex-
cept the last byte was different, and assuming the file was larger
than 1MB (so the MD5 digests are the same but the files are actu-
ally different), the three files would be stored as:

__TOPDIR__/pool/1/2/3/123456789abcdef0123456789abcdef0
__TOPDIR__/pool/1/2/3/123456789abcdef0123456789abcdef0_0
__TOPDIR__/pool/1/2/3/123456789abcdef0123456789abcdef0_1

__TOPDIR__/cpool
All compressed files from PC backups are stored below
__TOPDIR__/cpool. Its layout is the same as __TOPDIR__/pool, and
the hashing function is the same (and, importantly, based on the
uncompressed file, not the compressed file).

__TOPDIR__/pc/$host
For each PC $host, all the backups for that PC are stored below the
directory __TOPDIR__/pc/$host. This directory contains the follow-
ing files:

LOG Current log file for this PC from BackupPC_dump.

LOG.MMYYYY or LOG.MMYYYY.z
Last month's log file. Log files are aged monthly and com-
pressed (if compression is enabled), and old LOG files are
deleted. In earlier versions of BackupPC these files used to
have a suffix of 0, 1, ....

XferERR or XferERR.z
Output from the transport program (ie: smbclient, tar, rsync or
ftp) for the most recent failed backup.

XferLOG or XferLOG.z
Output from the transport program (ie: smbclient, tar, rsync or
ftp) for the current backup.

nnn (an integer)
Backups are in directories numbered sequentially starting at 0.
Below each backup directory are the inodes (in nnn/inode) and
the reference counts for this backup are in nnn/refCnt.

refCnt
The host's reference count database is stored below the refCnt
directory.

XferLOG.nnn or XferLOG.nnn.z
Output from the transport program (ie: smbclient, tar, rsync or
ftp) corresponding to backup number nnn.

RestoreInfo.nnn
Information about restore request #nnn including who, what,
when, and why. This file is in Data::Dumper format. (Note that
the restore numbers are not related to the backup number.)

RestoreLOG.nnn.z
Output from smbclient, tar or rsync during restore #nnn. (Note
that the restore numbers are not related to the backup number.)

ArchiveInfo.nnn
Information about archive request #nnn including who, what,
when, and why. This file is in Data::Dumper format. (Note that
the archive numbers are not related to the restore or backup
number.)

ArchiveLOG.nnn.z
Output from archive #nnn. (Note that the archive numbers are
not related to the backup or restore number.)

config.pl
Old location of optional configuration settings specific to
this host. Settings in this file override the main configura-
tion file. In new versions of BackupPC the per-host configura-
tion files are stored in __CONFDIR__/pc/HOST.pl.

backups
A tab-delimited ascii table listing information about each suc-
cessful backup, one per row. The columns are:

num The backup number, an integer that starts at 0 and incre-
ments for each successive backup. The corresponding backup
is stored in the directory num (eg: if this field is 5,
then the backup is stored in __TOPDIR__/pc/$host/5).

typeSet to "full" or "incr" for full or incremental backup.

startTime
Start time of the backup in unix seconds.

endTime
Stop time of the backup in unix seconds.

nFiles
Number of files backed up (as reported by smbclient, tar,
rsync or ftp).

sizeTotal file size backed up (as reported by smbclient, tar,
rsync or ftp).

nFilesExist
Number of files that were already in the pool (as deter-
mined by BackupPC_dump).

sizeExist
Total size of files that were already in the pool (as de-
termined by BackupPC_dump).

nFilesNew
Number of files that were not in the pool (as determined by
BackupPC_dump).

sizeNew
Total size of files that were not in the pool (as deter-
mined by BackupPC_dump).

xferErrs
Number of errors or warnings from smbclient, tar, rsync or
ftp.

xferBadFile
Number of errors from smbclient that were bad file errors
(zero otherwise).

xferBadShare
Number of errors from smbclient that were bad share errors
(zero otherwise).

tarErrs
Number of errors from BackupPC_tarExtract.

compress
The compression level used on this backup. Zero or empty
means no compression.

sizeExistComp
Total compressed size of files that were already in the
pool (as determined by BackupPC_dump).

sizeNewComp
Total compressed size of files that were not in the pool
(as determined by BackupPC_dump).

noFill
Set if this backup has not been filled - it just includes
the deltas from the next backup necessary to reconstruct
this backup.

fillFromNum
If this backup was filled (ie: noFill is 0) then this is
the number of the backup that it was filled from

mangle
Set if this backup has mangled filenames and attributes.
Always true for backups in v1.4.0 and above. False for all
backups prior to v1.4.0.

xferMethod
Set to the value of $Conf{XferMethod} when this dump was
done.

level
The level of this dump. A full dump is level 0. Currently
incrementals are 1. In V4+ multi-level incrementals are no
longer supported, so this is just a 0 or 1.

charset
The client charset when this backup was made.

version
The BackupPC version when this backup was made.

inodeLast
The last inode number used in this backup.

keepIf set this backup won't be deleted.

share2path
Saves the value of $Conf{ClientShareName2Path} via
Data::Dumper (with some tabs, newlines and % characters re-
placed with %xx) so that the actual client path for each
share can be displayed when browsing.

restores
A tab-delimited ascii table listing information about each re-
quested restore, one per row. The columns are:

num Restore number (matches the suffix of the RestoreInfo.nnn
and RestoreLOG.nnn.z file), unrelated to the backup number.

startTime
Start time of the restore in unix seconds.

endTime
End time of the restore in unix seconds.

result
Result (ok or failed).

errorMsg
Error message if restore failed.

nFiles
Number of files restored.

sizeSize in bytes of the restored files.

tarCreateErrs
Number of errors from BackupPC_tarCreate during restore.

xferErrs
Number of errors from smbclient, tar, rsync or ftp during
restore.

archives
A tab-delimited ascii table listing information about each re-
quested archive, one per row. The columns are:

num Archive number (matches the suffix of the ArchiveInfo.nnn
and ArchiveLOG.nnn.z file), unrelated to the backup or re-
store number.

startTime
Start time of the restore in unix seconds.

endTime
End time of the restore in unix seconds.

result
Result (ok or failed).

errorMsg
Error message if archive failed.

Compressed file format
The compressed file format is as generated by Compress::Zlib::deflate with
one minor, but important, tweak. Since Compress::Zlib::inflate fully in-
flates its argument in memory, it could take large amounts of memory if it
was inflating a highly compressed file. For example, a 200MB file of 0x0
bytes compresses to around 200K bytes. If Compress::Zlib::inflate was
called with this single 200K buffer, it would need to allocate 200MB of
memory to return the result.

BackupPC watches how efficiently a file is compressing. If a big file has
very high compression (meaning it will use too much memory when it is in-
flated), BackupPC calls the flush() method, which gracefully completes the
current compression. BackupPC then starts another deflate and simply ap-
pends the output file. So the BackupPC compressed file format is one or
more concatenated deflations/flushes. The specific ratios that BackupPC
uses is that if a 6MB chunk compresses to less than 64K then a flush will
be done.

Back to the example of the 200MB file of 0x0 bytes. Adding flushes every
6MB adds only 200 or so bytes to the 200K output. So the storage cost of
flushing is negligible.

To easily decompress a BackupPC compressed file, the script BackupPC_zcat
can be found in __INSTALLDIR__/bin. For each filename argument it inflates
the file and writes it to stdout.

Rsync checksum caching
Rsync checksum caching is not implemented in V4. That's because a full
backup with rsync in V4 uses client-side whole-file checksums during a full
backup, meaning that the server doesn't need to send block-level digests on
every full backup.

The rest of this section applies to V3.

An incremental backup with rsync compares attributes on the client with the
last full backup. Any files with identical attributes are skipped. In V3,
a full backup with rsync sets the --ignore-times option, which causes every
file to be examined independent of attributes.

Each file is examined by generating block checksums (default 2K blocks) on
the receiving side (that's the BackupPC side), sending those checksums to
the client, where the remote rsync matches those checksums with the corre-
sponding file. The matching blocks and new data is sent back, allowing the
client file to be reassembled. A checksum for the entire file is sent to
as an extra check the the reconstructed file is correct.

This results in significant disk IO and computation for BackupPC: every
file in a full backup, or any file with non-matching attributes in an in-
cremental backup, needs to be uncompressed, block checksums computed and
sent. Then the receiving side reassembles the file and has to verify the
whole-file checksum. Even if the file is identical, prior to 2.1.0, Back-
upPC had to read and uncompress the file twice, once to compute the block
checksums and later to verify the whole-file checksum.

Filename mangling
Backup filenames are stored in "mangled" form. Each node of a path is pre-
ceded by "f" (mnemonic: file), and special characters (\n, \r, % and /) are
URI-encoded as "%xx", where xx is the ascii character's hex value. So
c:/craig/example.txt is now stored as fc/fcraig/fexample.txt.

This was done mainly so metadata could be stored alongside the backup files
without name collisions. In particular, the attributes for the files in a
directory are stored in a file called "attrib", and mangling avoids file-
name collisions (I discarded the idea of having a duplicate directory tree
for every backup just to store the attributes). Other metadata (eg: rsync
checksums) could be stored in filenames preceded by, eg, "c". There are two
other benefits to mangling: the share name might contain "/" (eg:
"/home/craig" for tar transport), and I wanted that represented as a single
level in the storage tree.

The CGI script undoes the mangling, so it is invisible to the user.

Special files
Linux/unix file systems support several special file types: symbolic links,
character and block device files, fifos (pipes) and unix-domain sockets.
All except unix-domain sockets are supported by BackupPC (there's no point
in backing up or restoring unix-domain sockets since they only have meaning
after a process creates them). Symbolic links are stored as a plain file
whose contents are the contents of the link (not the file it points to).
This file is compressed and pooled like any normal file. Character and
block device files are also stored as plain files, whose contents are two
integers separated by a comma; the numbers are the major and minor device
number. These files are compressed and pooled like any normal file. Fifo
files are stored as empty plain files (which are not pooled since they have
zero size). In all cases, the original file type is stored in the attrib
file so it can be correctly restored.

Hardlinks are supported. In V4, file metadata include an inode number and
a link count. Any file with more than one link points at the inode infor-
mation stored below the backup directory in the inode directory. That di-
rectory contains a tree of up to 16K attrib files based on bits 10-23 of
the inode number. In particular, the directory name uses bits 17-23, and
the attrib filename includes bits 10-16. The key (index) in the attrib
file is the hex inode number. The original file metadata's link count
might not be accurate; it's more a flag (>1) for when to look up the inode
information. The correct link count is stored in the inode.

In V3, hardlinks are stored in a similar manner to symlinks. When GNU tar
first encounters a file with more than one link (ie: hardlinks) it dumps it
as a regular file. When it sees the second and subsequent hardlinks to the
same file, it dumps just the hardlink information. BackupPC correctly rec-
ognizes these hardlinks and stores them just like symlinks: a regular text
file whose contents is the path of the file linked to. The CGI script will
download the original file when you click on a hardlink.

Also, BackupPC_tarCreate has enough magic to re-create the hardlinks dynam-
ically based on whether or not the original file and hardlinks are both in-
cluded in the tar file. For example, imagine a/b/x is a hardlink to a/c/y.
If you use BackupPC_tarCreate to restore directory a, then the tar file
will include a/b/x as the original file and a/c/y will be a hardlink to
a/b/x. If, instead you restore a/c, then the tar file will include a/c/y
as the original file, not a hardlink.

Attribute file format
V4 attrib files
The attribute file format is new in V4. Every backup directory con-
tains an attrib file, which is zero length and its name includes the
MD5 pool digest, eg:

attrib_33fe8f9ae2f5cedbea63b9d3ea767ac0

The digest is used to look up the contents in the V4 cpool, eg:

__TOPDIR__/cpool/32/fe/33fe8f9ae2f5cedbea63b9d3ea767ac0

For inode attrib files, bits 17-23 (XX in hex) of the inode number are
used for the directory name, and the attrib filename includes bits
10-16 (YY in hex), so relative to the backup directory:

inode/XX/attribYY_33fe8f9ae2f5cedbea63b9d3ea767ac0

An empty attrib file has the name "attrib_0" (or "attribYY_0" for in-
odes).

The attrib file starts with a magic number, followed by the concatena-
tion of the following information for each file (all integers are
stored in perl's pack "w" format (variable length base 128)):

* Filename length, followed by the filename

* Count of extended attributes

* The unix file type, mtime, mode, uid, gid, size, inode number, com-
press, number of links

* MD5 digest length, followed by the digest contents

* Each extended attribute (length of xattr name, length of xattr
value, name, value)

V3 attrib files
The unix attributes for the contents of a directory (all the files and
directories in that directory) are stored in a file called attrib.
There is a single attrib file for each directory in a backup. For ex-
ample, if c:/craig contains a single file c:/craig/example.txt, that
file would be stored as fc/fcraig/fexample.txt and there would be an
attribute file in fc/fcraig/attrib (and also fc/attrib and ./attrib).
The file fc/fcraig/attrib would contain a single entry containing the
attributes for fc/fcraig/fexample.txt.

The attrib file starts with a magic number, followed by the concatena-
tion of the following information for each file:

* Filename length in perl's pack "w" format (variable length base
128).

* Filename.

* The unix file type, mode, uid, gid and file size divided by 4GB and
file size modulo 4GB (type mode uid gid sizeDiv4GB sizeMod4GB), in
perl's pack "w" format (variable length base 128).

* The unix mtime (unix seconds) in perl's pack "N" format (32 bit in-
teger).

The attrib file is also compressed if compression is enabled. See the
lib/BackupPC/Attrib.pm module for full details.

Attribute files are pooled just like normal backup files. This saves
space if all the files in a directory have the same attributes across
multiple backups, which is common.

Optimizations
BackupPC doesn't care about the access time of files in the pool since it
saves attribute metadata separate from the files. Since BackupPC mostly
does reads from disk, maintaining the access time of files generates a lot
of unnecessary disk writes. So, provided BackupPC has a dedicated data
disk, you should consider mounting BackupPC's data directory with the noat-
ime (or, with Linux kernels >=2.6.20, relatime) attribute (see mount(1)).

Some Limitations
BackupPC isn't perfect (but it is getting better). Please see <http://back-
uppc.sourceforge.net/faq/limitations.html> for a discussion of some of
BackupPC's limitations. (Note, this is old and we should move this to the
Github Wiki.)

Security issues
Please see <http://backuppc.sourceforge.net/faq/security.html> for a dis-
cussion of some of various security issues. (Note, this is old and we
should move this to the Github Wiki.)

Configuration File
The BackupPC configuration file resides in __CONFDIR__/config.pl. Optional
per-PC configuration files reside in __CONFDIR__/pc/$host.pl (or
__TOPDIR__/pc/$host/config.pl in non-FHS versions of BackupPC). This file
can be used to override settings just for a particular PC.

Modifying the main configuration file
The configuration file is a perl script that is executed by BackupPC, so
you should be careful to preserve the file syntax (punctuation, quotes etc)
when you edit it. Specifically, preserving quotes means you should never
use undef for configuration parameters that expect string values. An empty
string ('') should be used in this case. It is recommended that you use
CVS, RCS or some other method of source control for changing config.pl.

BackupPC reads or re-reads the main configuration file and the hosts file
in three cases:

* Upon startup.

* When BackupPC is sent a HUP (-1) signal. Assuming you installed the
init.d script, you can also do this with "/etc/init.d/backuppc reload".

* When the modification time of config.pl file changes. BackupPC checks
the modification time once during each regular wakeup.

Whenever you change the configuration file you can either do a kill -HUP
BackupPC_pid or simply wait until the next regular wakeup period.

Each time the configuration file is re-read a message is reported in the
LOG file, so you can tail it (or view it via the CGI interface) to make
sure your kill -HUP worked. Errors in parsing the configuration file are
also reported in the LOG file.

The optional per-PC configuration file (__CONFDIR__/pc/$host.pl or
__TOPDIR__/pc/$host/config.pl in non-FHS versions of BackupPC) is read
whenever it is needed by BackupPC_dump, BackupPC_restore and others.

Configuration Parameters
The configuration parameters are divided into five general groups. The
first group (general server configuration) provides general configuration
for BackupPC. The next two groups describe what to backup, when to do it,
and how long to keep it. The fourth group are settings for email re-
minders, and the final group contains settings for the CGI interface.

All configuration settings in the second through fifth groups can be over-
ridden by the per-PC config.pl file.

General server configuration
$Conf{ServerHost} = '';
Host name on which the BackupPC server is running.

$Conf{ServerPort} = -1;
TCP port number on which the BackupPC server listens for and accepts
connections. Normally this should be disabled (set to -1). The TCP
port is only needed if apache runs on a different machine from Back-
upPC. In that case, set this to any spare port number over 1024 (eg:
2359). If you enable the TCP port, make sure you set $Conf{ServerMes-
gSecret} too!

$Conf{ServerMesgSecret} = '';
Shared secret to make the TCP port secure. Set this to a hard to guess
string if you enable the TCP port (ie: $Conf{ServerPort} > 0).

To avoid possible attacks via the TCP socket interface, every client
message is protected by an MD5 digest. The MD5 digest includes four
items:
- a seed that is sent to the client when the connection opens
- a sequence number that increments for each message
- a shared secret that is stored in $Conf{ServerMesgSecret}
- the message itself.

The message is sent in plain text preceded by the MD5 digest. A
snooper can see the plain-text seed sent by BackupPC and plain-text
message from the client, but cannot construct a valid MD5 digest since
the secret $Conf{ServerMesgSecret} is unknown. A replay attack is not
possible since the seed changes on a per-connection and per-message ba-
sis.

$Conf{MyPath} = '/bin';
PATH setting for BackupPC. An explicit value is necessary for taint
mode. Value shouldn't matter too much since all execs use explicit
paths. However, taint mode in perl will complain if this directory is
world writable.

$Conf{UmaskMode} = 027;
Permission mask for directories and files created by BackupPC. Default
value prevents any access from group other, and prevents group write.

$Conf{WakeupSchedule} = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15,
16, 17, 18, 19, 20, 21, 22, 23];
Times at which we wake up, check all the PCs, and schedule necessary
backups. Times are measured in hours since midnight local time. Can
be fractional if necessary (eg: 4.25 means 4:15am).

If the hosts you are backing up are always connected to the network you
might have only one or two wakeups each night. This will keep the
backup activity after hours. On the other hand, if you are backing up
laptops that are only intermittently connected to the network you will
want to have frequent wakeups (eg: hourly) to maximize the chance that
each laptop is backed up.

Examples:

$Conf{WakeupSchedule} = [22.5]; # once per day at 10:30 pm.
$Conf{WakeupSchedule} = [2,4,6,8,10,12,14,16,18,20,22]; # every 2 hours

The default value is every hour except midnight.

The first entry of $Conf{WakeupSchedule} is when BackupPC_nightly is
run. You might want to re-arrange the entries in $Conf{WakeupSchedule}
(they don't have to be ascending) so that the first entry is when you
want BackupPC_nightly to run (eg: when you don't expect a lot of regu-
lar backups to run).

$Conf{PoolV3Enabled} = 0;
If a V3 pool exists (ie: an upgrade) set this to 1. This causes the V3
pool to be checked for matches if there are no matches in the V4 pool.

For new installations, this should be set to 0.

$Conf{MaxBackups} = 4;
Maximum number of simultaneous backups to run. If there are no user
backup requests then this is the maximum number of simultaneous back-
ups.

$Conf{MaxUserBackups} = 4;
Additional number of simultaneous backups that users can run. As many
as $Conf{MaxBackups} + $Conf{MaxUserBackups} requests can run at the
same time.

$Conf{MaxPendingCmds} = 15;
Maximum number of pending link commands. New backups will only be
started if there are no more than $Conf{MaxPendingCmds} plus
$Conf{MaxBackups} number of pending link commands, plus running jobs.
This limit is to make sure BackupPC doesn't fall too far behind in run-
ning BackupPC_link commands.

$Conf{CmdQueueNice} = 10;
Nice level at which CmdQueue commands (eg: BackupPC_link and Back-
upPC_nightly) are run at.

$Conf{MaxBackupPCNightlyJobs} = 2;
How many BackupPC_nightly processes to run in parallel.

Each night, at the first wakeup listed in $Conf{WakeupSchedule}, Back-
upPC_nightly is run. Its job is to remove unneeded files in the pool,
ie: files that only have one link. To avoid race conditions, Back-
upPC_nightly and BackupPC_link cannot run at the same time. Starting
in v3.0.0, BackupPC_nightly can run concurrently with backups (Back-
upPC_dump).

So to reduce the elapsed time, you might want to increase this setting
to run several BackupPC_nightly processes in parallel (eg: 4, or even
8).

$Conf{BackupPCNightlyPeriod} = 1;
How many days (runs) it takes BackupPC_nightly to traverse the entire
pool. Normally this is 1, which means every night it runs, it does
traverse the entire pool removing unused pool files.

Other valid values are 2, 4, 8, 16. This causes BackupPC_nightly to
traverse 1/2, 1/4, 1/8 or 1/16th of the pool each night, meaning it
takes 2, 4, 8 or 16 days to completely traverse the pool. The advan-
tage is that each night the running time of BackupPC_nightly is reduced
roughly in proportion, since the total job is split over multiple days.
The disadvantage is that unused pool files take longer to get deleted,
which will slightly increase disk usage.

Note that even when $Conf{BackupPCNightlyPeriod} > 1, BackupPC_nightly
still runs every night. It just does less work each time it runs.

Examples:

$Conf{BackupPCNightlyPeriod} = 1; # entire pool is checked every night

$Conf{BackupPCNightlyPeriod} = 2; # two days to complete pool check
# (different half each night)

$Conf{BackupPCNightlyPeriod} = 4; # four days to complete pool check
# (different quarter each night)

$Conf{PoolSizeNightlyUpdatePeriod} = 16;
The total size of the files in the new V4 pool is updated every night
when BackupPC_nightly runs BackupPC_refCountUpdate. Instead of adding
up the size of every pool file, it just updates the pool size total
when files are added to or removed from the pool.

To make sure these cumulative pool file sizes stay accurate, we recom-
pute the V4 pool size for a portion of the pool each night from
scratch, ie: by checking every file in that portion of the pool.

$Conf{PoolSizeNightlyUpdatePeriod} sets how many nights it takes to
completely update the V4 pool size. It can be set to:
0: never do a full refresh; simply maintain the cumulative sizes
when files are added or deleted (fastest option)
1: recompute all the V4 pool size every night (slowest option)
2: recompute 1/2 the V4 pool size every night
4: recompute 1/4 the V4 pool size every night
8: recompute 1/8 the V4 pool size every night
16: recompute 1/16 the V4 pool size every night
(2nd fastest option; ensures the pool files sizes
stay accurate after a few day, in case the relative
upgrades miss a file)

$Conf{PoolNightlyDigestCheckPercent} = 1;
Integrity check the pool files by confirming the md5 digest of the con-
tents matches their file name. Because the pool is very large, only
check a small random percentage of the pool files each night.

This is check if there has been any server file system corruption.

The default value of 1% means approximately 30% of the pool files will
be checked each month, although the actual number will be a bit less
since some files might be checked more than once in that time. If Back-
upPC_nightly takes too long, you could reduce this value.

$Conf{RefCntFsck} = 1;
Reference counts of pool files are computed per backup by accumulating
the relative changes. That means, however, that any error will never
be corrected. To be more conservative, we do a periodic full-redo of
the backup reference counts (called an "fsck"). $Conf{RefCntFsck} con-
trols how often this is done:

0: no additional fsck
1: do an fsck on the last backup if it is from a full backup
2: do an fsck on the last two backups always
3: do a full fsck on all the backups

$Conf{RefCntFsck} = 1 is the recommended setting.

$Conf{MaxOldLogFiles} = 14;
Maximum number of log files we keep around in log directory. These
files are aged nightly. A setting of 14 means the log directory will
contain about 2 weeks of old log files, in particular at most the files
LOG, LOG.0, LOG.1, ... LOG.13 (except today's LOG, these files will
have a .z extension if compression is on).

If you decrease this number after BackupPC has been running for a while
you will have to manually remove the older log files.

$Conf{DfPath} = '';
Full path to the df command. Security caution: normal users should not
allowed to write to this file or directory.

$Conf{DfCmd} = '$dfPath $topDir';
Command to run df. The following variables are substituted at
run-time:

$dfPath path to df ($Conf{DfPath})
$topDir top-level BackupPC data directory

Note: all Cmds are executed directly without a shell, so the prog name
needs to be a full path and you can't include shell syntax like redi-
rection and pipes; put that in a script if you need it.

$Conf{DfInodeUsageCmd} = '$dfPath -i $topDir';
Command to run df to get inode % usage. The following variables are
substituted at run-time:

$dfPath path to df ($Conf{DfPath})
$topDir top-level BackupPC data directory

Note: all Cmds are executed directly without a shell, so the prog name
needs to be a full path and you can't include shell syntax like redi-
rection and pipes; put that in a script if you need it.

$Conf{SplitPath} = '';
$Conf{ParPath} = '';
$Conf{CatPath} = '';
$Conf{GzipPath} = '';
$Conf{Bzip2Path} = '';
Full path to various commands for archiving

$Conf{DfMaxUsagePct} = 95;
Maximum threshold for disk utilization on the __TOPDIR__ filesystem.
If the output from $Conf{DfCmd} reports a percentage larger than this
number then no new regularly scheduled backups will be run. However,
user requested backups (which are usually incremental and tend to be
small) are still performed, independent of disk usage. Also, currently
running backups will not be terminated when the disk usage exceeds this
number.

$Conf{DfMaxInodeUsagePct} = 95;
Maximum threshold for inode utilization on the __TOPDIR__ filesystem.
If the output from $Conf{DfInodeUsageCmd} reports a percentage larger
than this number then no new regularly scheduled backups will be run.
However, user requested backups (which are usually incremental and tend
to be small) are still performed, independent of disk usage. Also,
currently running backups will not be terminated when the disk inode
usage exceeds this number.

$Conf{DHCPAddressRanges} = [];
List of DHCP address ranges we search looking for PCs to backup. This
is an array of hashes for each class C address range. This is only
needed if hosts in the conf/hosts file have the dhcp flag set.

Examples:

# to specify 192.10.10.20 to 192.10.10.250 as the DHCP address pool
$Conf{DHCPAddressRanges} = [
{
ipAddrBase => '192.10.10',
first => 20,
last => 250,
},
];
# to specify two pools (192.10.10.20-250 and 192.10.11.10-50)
$Conf{DHCPAddressRanges} = [
{
ipAddrBase => '192.10.10',
first => 20,
last => 250,
},
{
ipAddrBase => '192.10.11',
first => 10,
last => 50,
},
];

$Conf{BackupPCUser} = '';
The BackupPC user.

$Conf{TopDir} = '';
$Conf{ConfDir} = '';
$Conf{LogDir} = '';
$Conf{RunDir} = '';
$Conf{InstallDir} = '';
$Conf{CgiDir} = '';
Important installation directories:

TopDir - where all the backup data is stored
ConfDir - where the main config and hosts files resides
LogDir - where log files and other transient information resides
RunDir - where pid and sock files reside
InstallDir - where the bin, lib and doc installation dirs reside.
Note: you cannot change this value since all the
perl scripts include this path. You must reinstall
with configure.pl to change InstallDir.
CgiDir - Apache CGI directory for BackupPC_Admin

Note: it is STRONGLY recommended that you don't change the values here.
These are set at installation time and are here for reference and are
used during upgrades.

Instead of changing TopDir here it is recommended that you use a sym-
bolic link to the new location, or mount the new BackupPC store at the
existing $Conf{TopDir} setting.

$Conf{BackupPCUserVerify} = 1;
Whether BackupPC and the CGI script BackupPC_Admin verify that they are
really running as user $Conf{BackupPCUser}. If this flag is set and
the effective user id (euid) differs from $Conf{BackupPCUser} then both
scripts exit with an error. This catches cases where BackupPC might be
accidentally started as root or the wrong user, or if the CGI script is
not installed correctly.

$Conf{HardLinkMax} = 31999;
Maximum number of hardlinks supported by the $TopDir file system that
BackupPC uses. Most linux or unix file systems should support at least
32000 hardlinks per file, or 64000 in other cases. If a pool file al-
ready has this number of hardlinks, a new pool file is created so that
new hardlinks can be accommodated. This limit will only be hit if an
identical file appears at least this number of times across all the
backups.

$Conf{PerlModuleLoad} = undef;
Advanced option for asking BackupPC to load additional perl modules.
Can be a list (arrayref) of module names to load at startup.

$Conf{ServerInitdPath} = '';
$Conf{ServerInitdStartCmd} = '';
Path to init.d script and command to use that script to start the
server from the CGI interface. The following variables are substituted
at run-time:

$sshPath path to ssh ($Conf{SshPath})
$serverHost same as $Conf{ServerHost}
$serverInitdPath path to init.d script ($Conf{ServerInitdPath})

Example:

$Conf{ServerInitdPath} = '/etc/init.d/backuppc'; $Conf{ServerInitd-
StartCmd} = '$sshPath -q -x -l root $serverHost'
. ' $serverInitdPath start'
. ' < /dev/null >& /dev/null';

Note: all Cmds are executed directly without a shell, so the prog name
needs to be a full path and you can't include shell syntax like redi-
rection and pipes; put that in a script if you need it.

What to backup and when to do it
$Conf{FullPeriod} = 6.97;
Minimum period in days between full backups. A full dump will only be
done if at least this much time has elapsed since the last full dump,
and at least $Conf{IncrPeriod} days has elapsed since the last success-
ful dump.

Typically this is set slightly less than an integer number of days. The
time taken for the backup, plus the granularity of $Conf{WakeupSched-
ule} will make the actual backup interval a bit longer.

$Conf{IncrPeriod} = 0.97;
Minimum period in days between incremental backups (a user requested
incremental backup will be done anytime on demand).

Typically this is set slightly less than an integer number of days. The
time taken for the backup, plus the granularity of $Conf{WakeupSched-
ule} will make the actual backup interval a bit longer.

$Conf{FillCycle} = 0;
In V4+, full/incremental backups are decoupled from whether the stored
backup is filled/unfilled.

To mimic V3 behaviour, if $Conf{FillCycle} is set to zero then fill/un-
filled will continue to match full/incremental: full backups will re-
mained filled, and incremental backups will be unfilled. (However, the
most recent backup is always filled, whether it is full or incremen-
tal.) This is the recommended setting to keep things simple: since the
backup expiry is actually done based on filled/unfilled (not full/in-
cremental), keeping them synched makes it easier to understand the ex-
piry settings.

If you plan to do incremental-only backups (ie: set FullPeriod to a
very large value), then you should set $Conf{FillCycle} to how often
you want a stored backup to be filled. For example, if $Conf{FillCy-
cle} is set to 7, then every 7th backup will be filled (whether or not
the corresponding backup was a full or not).

There are two reasons you will want a non-zero $Conf{FillCycle} setting
when you are only doing incrementals:

- a filled backup is a starting point for merging deltas when you restore
or view backups. So having periodic filled backups makes it more
efficient to view or restore older backups.

- more importantly, in V4+, deleting backups is done based on Fill/Unfilled,
not whether the original backup was full/incremental. If there aren't any
filled backups (other than the most recent), then the $Conf{FullKeepCnt}
and related settings won't have any effect.

$Conf{FullKeepCnt} = 1;
Number of filled backups to keep. Must be >= 1.

The most recent backup (which is always filled) doesn't count when
checking $Conf{FullKeepCnt}. So if you specify $Conf{FullKeepCnt} = 1
then that means keep one full backup in addition to the most recent
backup (which might be a filled incr or full).

Note: Starting in V4+, deleting backups is done based on Fill/Unfilled,
not whether the original backup was full/incremental. For backward com-
patibility, these parameters continue to be called FullKeepCnt, rather
than FilledKeepCnt. If $Conf{FillCycle} is 0, then full backups con-
tinue to be filled, so the terms are interchangeable. For V3 backups,
the expiry settings have their original meanings.

In the steady state, each time a full backup completes successfully the
oldest one is removed. If this number is decreased, the extra old
backups will be removed.

Exponential backup expiry is also supported. This allows you to spec-
ify:

- num fulls to keep at intervals of 1 * $Conf{FillCycle}, followed by
- num fulls to keep at intervals of 2 * $Conf{FillCycle},
- num fulls to keep at intervals of 4 * $Conf{FillCycle},
- num fulls to keep at intervals of 8 * $Conf{FillCycle},
- num fulls to keep at intervals of 16 * $Conf{FillCycle},

and so on. This works by deleting every other full as each expiry
boundary is crossed. Note: if $Conf{FillCycle} is 0, then
$Conf{FullPeriod} is used instead in these calculations.

Exponential expiry is specified using an array for $Conf{FullKeepCnt}:

$Conf{FullKeepCnt} = [4, 2, 3];

Entry #n specifies how many fulls to keep at an interval of 2^n *
$Conf{FillCycle} (ie: 1, 2, 4, 8, 16, 32, ...).

The example above specifies keeping 4 of the most recent full backups
(1 week interval) two full backups at 2 week intervals, and 3 full
backups at 4 week intervals, eg:

full 0 19 weeks old \
full 1 15 weeks old >--- 3 backups at 4 * $Conf{FillCycle}
full 2 11 weeks old /
full 3 7 weeks old \____ 2 backups at 2 * $Conf{FillCycle}
full 4 5 weeks old /
full 5 3 weeks old \
full 6 2 weeks old \___ 4 backups at 1 * $Conf{FillCycle}
full 7 1 week old /
full 8 current /

On a given week the spacing might be less than shown as each backup
ages through each expiry period. For example, one week later, a new
full is completed and the oldest is deleted, giving:

full 0 16 weeks old \
full 1 12 weeks old >--- 3 backups at 4 * $Conf{FillCycle}
full 2 8 weeks old /
full 3 6 weeks old \____ 2 backups at 2 * $Conf{FillCycle}
full 4 4 weeks old /
full 5 3 weeks old \
full 6 2 weeks old \___ 4 backups at 1 * $Conf{FillCycle}
full 7 1 week old /
full 8 current /

You can specify 0 as a count (except in the first entry), and the array
can be as long as you wish. For example:

$Conf{FullKeepCnt} = [4, 0, 4, 0, 0, 2];

This will keep 10 full dumps, 4 most recent at 1 * $Conf{FillCycle},
followed by 4 at an interval of 4 * $Conf{FillCycle} (approx 1 month
apart), and then 2 at an interval of 32 * $Conf{FillCycle} (approx 7-8
months apart).

Example: these two settings are equivalent and both keep just the four
most recent full dumps:

$Conf{FullKeepCnt} = 4;
$Conf{FullKeepCnt} = [4];

$Conf{FullKeepCntMin} = 1;
$Conf{FullAgeMax} = 180;
Very old full backups are removed after $Conf{FullAgeMax} days. How-
ever, we keep at least $Conf{FullKeepCntMin} full backups no matter how
old they are.

Note that $Conf{FullAgeMax} will be increased to $Conf{FullKeepCnt}
times $Conf{FillCycle} if $Conf{FullKeepCnt} specifies enough full
backups to exceed $Conf{FullAgeMax}.

$Conf{IncrKeepCnt} = 6;
Number of incremental backups to keep. Must be >= 1.

Note: Starting in V4+, deleting backups is done based on Fill/Unfilled,
not whether the original backup was full/incremental. For historical
reasons these parameters continue to be called IncrKeepCnt, rather than
UnfilledKeepCnt. If $Conf{FillCycle} is 0, then incremental backups
continue to be unfilled, so the terms are interchangeable. For V3
backups, the expiry settings have their original meanings.

In the steady state, each time an incr backup completes successfully
the oldest one is removed. If this number is decreased, the extra old
backups will be removed.

$Conf{IncrKeepCntMin} = 1;
$Conf{IncrAgeMax} = 30;
Very old incremental backups are removed after $Conf{IncrAgeMax} days.
However, we keep at least $Conf{IncrKeepCntMin} incremental backups no
matter how old they are.

$Conf{BackupsDisable} = 0;
Disable all full and incremental backups. These settings are useful
for a client that is no longer being backed up (eg: a retired machine),
but you wish to keep the last backups available for browsing or restor-
ing to other machines.

There are three values for $Conf{BackupsDisable}:

0 Backups are enabled.

1 Don't do any regular backups on this client. Manually
requested backups (via the CGI interface) will still occur.

2 Don't do any backups on this client. Manually requested
backups (via the CGI interface) will be ignored.

In versions prior to 3.0 Backups were disabled by setting $Conf{FullPe-
riod} to -1 or -2.

$Conf{RestoreInfoKeepCnt} = 10;
Number of restore logs to keep. BackupPC remembers information about
each restore request. This number per client will be kept around be-
fore the oldest ones are pruned.

Note: files/dirs delivered via Zip or Tar downloads don't count as re-
stores. Only the first restore option (where the files and dirs are
written to the host) count as restores that are logged.

$Conf{ArchiveInfoKeepCnt} = 10;
Number of archive logs to keep. BackupPC remembers information about
each archive request. This number per archive client will be kept
around before the oldest ones are pruned.

$Conf{BackupFilesOnly} = undef;
List of directories or files to backup. If this is defined, only these
directories or files will be backed up.

For Smb, only one of $Conf{BackupFilesExclude} and $Conf{Backup-
FilesOnly} can be specified per share. If both are set for a particular
share, then $Conf{BackupFilesOnly} takes precedence and $Conf{Backup-
FilesExclude} is ignored.

This can be set to a string, an array of strings, or, in the case of
multiple shares, a hash of strings or arrays. A hash is used to give a
list of directories or files to backup for each share (the share name
is the key). If this is set to just a string or array, and $Conf{Smb-
ShareName} contains multiple share names, then the setting is assumed
to apply all shares.

If a hash is used, a special key "*" means it applies to all shares
that don't have a specific entry.

Examples:

$Conf{BackupFilesOnly} = '/myFiles';
$Conf{BackupFilesOnly} = ['/myFiles']; # same as first example
$Conf{BackupFilesOnly} = ['/myFiles', '/important'];
$Conf{BackupFilesOnly} = {
'c' => ['/myFiles', '/important'], # these are for 'c' share
'd' => ['/moreFiles', '/archive'], # these are for 'd' share
};
$Conf{BackupFilesOnly} = {
'c' => ['/myFiles', '/important'], # these are for 'c' share
'*' => ['/myFiles', '/important'], # these are other shares
};

$Conf{BackupFilesExclude} = undef;
List of directories or files to exclude from the backup. For Smb, only
one of $Conf{BackupFilesExclude} and $Conf{BackupFilesOnly} can be
specified per share. If both are set for a particular share, then
$Conf{BackupFilesOnly} takes precedence and $Conf{BackupFilesExclude}
is ignored.

This can be set to a string, an array of strings, or, in the case of
multiple shares, a hash of strings or arrays. A hash is used to give a
list of directories or files to exclude for each share (the share name
is the key). If this is set to just a string or array, and $Conf{Smb-
ShareName} contains multiple share names, then the setting is assumed
to apply to all shares.

The exact behavior is determined by the underlying transport program,
smbclient or tar. For smbclient the exclude file list is passed into
the X option. Simple shell wild-cards using "*" or "?" are allowed.

For tar, if the exclude file contains a "/" it is assumed to be an-
chored at the start of the string. Since all the tar paths start with
"./", BackupPC prepends a "." if the exclude file starts with a "/".
Note that GNU tar version >= 1.13.7 is required for the exclude option
to work correctly. For linux or unix machines you should add "/proc"
to $Conf{BackupFilesExclude} unless you have specified --one-file-sys-
tem in $Conf{TarClientCmd} or --one-file-system in $Conf{RsyncArgs}.
Also, for tar, do not use a trailing "/" in the directory name: a
trailing "/" causes the name to not match and the directory will not be
excluded.

Users report that for smbclient you should specify a directory followed
by "/*", eg: "/proc/*", instead of just "/proc".

FTP servers are traversed recursively so excluding directories will
also exclude its contents. You can use the wildcard characters "*" and
"?" to define files for inclusion and exclusion. Both attributes
$Conf{BackupFilesOnly} and $Conf{BackupFilesExclude} can be defined for
the same share.

If a hash is used, a special key "*" means it applies to all shares
that don't have a specific entry.

Examples:

$Conf{BackupFilesExclude} = '/temp';
$Conf{BackupFilesExclude} = ['/temp']; # same as first example
$Conf{BackupFilesExclude} = ['/temp', '/winnt/tmp'];
$Conf{BackupFilesExclude} = {
'c' => ['/temp', '/winnt/tmp'], # these are for 'c' share
'd' => ['/junk', '/dont_back_this_up'], # these are for 'd' share
};
$Conf{BackupFilesExclude} = {
'c' => ['/temp', '/winnt/tmp'], # these are for 'c' share
'*' => ['/junk', '/dont_back_this_up'], # these are for other shares
};

$Conf{BlackoutBadPingLimit} = 3;
$Conf{BlackoutGoodCnt} = 7;
PCs that are always or often on the network can be backed up after
hours, to reduce PC, network and server load during working hours. For
each PC a count of consecutive good pings is maintained. Once a PC has
at least $Conf{BlackoutGoodCnt} consecutive good pings it is subject to
"blackout" and not backed up during hours and days specified by
$Conf{BlackoutPeriods}.

To allow for periodic rebooting of a PC or other brief periods when a
PC is not on the network, a number of consecutive bad pings is allowed
before the good ping count is reset. This parameter is $Conf{Blackout-
BadPingLimit}.

Note that bad and good pings don't occur with the same interval. If a
machine is always on the network, it will only be pinged roughly once
every $Conf{IncrPeriod} (eg: once per day). So a setting for
$Conf{BlackoutGoodCnt} of 7 means it will take around 7 days for a ma-
chine to be subject to blackout. On the other hand, if a ping is
failed, it will be retried roughly every time BackupPC wakes up, eg,
every one or two hours. So a setting for $Conf{BlackoutBadPingLimit} of
3 means that the PC will lose its blackout status after 3-6 hours of
unavailability.

To disable the blackout feature set $Conf{BlackoutGoodCnt} to a nega-
tive value. A value of 0 will make all machines subject to blackout.
But if you don't want to do any backups during the day it would be eas-
ier to just set $Conf{WakeupSchedule} to a restricted schedule.

$Conf{BlackoutPeriods} = [ ... ];
One or more blackout periods can be specified. If a client is subject
to blackout then no regular (non-manual) backups will be started during
any of these periods. hourBegin and hourEnd specify hours from mid-
night and weekDays is a list of days of the week where 0 is Sunday, 1
is Monday etc.

For example:

$Conf{BlackoutPeriods} = [
{
hourBegin => 7.0,
hourEnd => 19.5,
weekDays => [1, 2, 3, 4, 5],
},
];

specifies one blackout period from 7:00am to 7:30pm local time on
Mon-Fri.

The blackout period can also span midnight by setting hourBegin >
hourEnd, eg:

$Conf{BlackoutPeriods} = [
{
hourBegin => 7.0,
hourEnd => 19.5,
weekDays => [1, 2, 3, 4, 5],
},
{
hourBegin => 23,
hourEnd => 5,
weekDays => [5, 6],
},
];

This specifies one blackout period from 7:00am to 7:30pm local time on
Mon-Fri, and a second period from 11pm to 5am on Friday and Saturday
night.

$Conf{BackupZeroFilesIsFatal} = 1;
A backup of a share that has zero files is considered fatal. This is
used to catch miscellaneous Xfer errors that result in no files being
backed up. If you have shares that might be empty (and therefore an
empty backup is valid) you should set this flag to 0.

How to backup a client
$Conf{XferMethod} = 'smb';
What transport method to use to backup each host. If you have a mixed
set of WinXX and linux/unix hosts you will need to override this in the
per-PC config.pl.

The valid values are:

- 'smb': backup and restore via smbclient and the SMB protocol.
Easiest choice for WinXX.

- 'rsync': backup and restore via rsync (via rsh or ssh).
Best choice for linux/unix. Good choice also for WinXX.

- 'rsyncd': backup and restore via rsync daemon on the client.
Best choice for linux/unix if you have rsyncd running on
the client. Good choice also for WinXX.

- 'tar': backup and restore via tar, tar over ssh, rsh or nfs.
Good choice for linux/unix.

- 'archive': host is a special archive host. Backups are not done.
An archive host is used to archive other host's backups
to permanent media, such as tape, CDR or DVD.

$Conf{XferLogLevel} = 1;
Level of verbosity in Xfer log files. 0 means be quiet, 1 will give
one line per file, 2 will also show skipped files on incrementals,
higher values give more output.

$Conf{ClientCharset} = '';
Filename charset encoding on the client. BackupPC uses utf8 on the
server for filename encoding. If this is empty, then utf8 is assumed
and client filenames will not be modified. If set to a different en-
coding then filenames will converted to/from utf8 automatically during
backup and restore.

If the filenames displayed in the browser (eg: accents or special char-
acters) don't look right then it is likely you haven't set
$Conf{ClientCharset} correctly.

If you are using smbclient on a WinXX machine, smbclient will convert
to the "unix charset" setting in smb.conf. The default is utf8, in
which case leave $Conf{ClientCharset} empty since smbclient does the
right conversion.

If you are using rsync on a WinXX machine then it does no conversion.
A typical WinXX encoding for latin1/western europe is 'cp1252', so in
this case set $Conf{ClientCharset} to 'cp1252'.

On a linux or unix client, run "locale charmap" to see the client's
charset. Set $Conf{ClientCharset} to this value. A typical value for
english/US is 'ISO-8859-1'.

Do "perldoc Encode::Supported" to see the list of possible charset val-
ues. The FAQ at http://www.cl.cam.ac.uk/~mgk25/unicode.html is excel-
lent, and http://czyborra.com/charsets/iso8859.html provides more in-
formation on the iso-8859 charsets.

$Conf{ClientCharsetLegacy} = 'iso-8859-1';
Prior to 3.x no charset conversion was done by BackupPC. Backups were
stored in whatever charset the XferMethod provided - typically utf8 for
smbclient and the client's locale settings for rsync and tar (eg:
cp1252 for rsync on WinXX and perhaps iso-8859-1 with rsync on linux).
This setting tells BackupPC the charset that was used to store file-
names in old backups taken with BackupPC 2.x, so that non-ascii file-
names in old backups can be viewed and restored.

$Conf{ClientShareName2Path} = {};
Optionally map the share name to a different path on the client when
the xfer program is run. This can be used if you create a snapshot on
the client, which has a different path to the real share name. Or you
could use simpler names for the share instead of a path (eg: root,
home, usr) and map them to the real paths here.

This should be a hash whose key is the share name used in $Conf{Smb-
ShareName}, $Conf{TarShareName}, $Conf{RsyncShareName}, $Conf{FtpShare-
Name}, and the value is the string path name on the client. When a
backup or restore is done, if there is no matching entry in
$Conf{ClientShareName2Path}, or the entry is empty, then the share name
is not modified (so the default behavior is unchanged).

If you are using the rsyncd xfer method, then there is no need to use
this configuration setting (since rsyncd already supports mapping of
share names to paths in the client's rsyncd.conf).

Samba Configuration
$Conf{SmbShareName} = 'C$';
Name of the host share that is backed up when using SMB. This can be a
string or an array of strings if there are multiple shares per host.
Examples:

$Conf{SmbShareName} = 'c'; # backup 'c' share
$Conf{SmbShareName} = ['c', 'd']; # backup 'c' and 'd' shares

This setting only matters if $Conf{XferMethod} = 'smb'.

$Conf{SmbShareUserName} = '';
Smbclient share username. This is passed to smbclient's -U argument.

This setting only matters if $Conf{XferMethod} = 'smb'.

$Conf{SmbSharePasswd} = '';
Smbclient share password. This is passed to smbclient via its PASSWD
environment variable. There are several ways you can tell BackupPC the
smb share password. In each case you should be very careful about se-
curity. If you put the password here, make sure that this file is not
readable by regular users! See the "Setting up config.pl" section in
the documentation for more information.

This setting only matters if $Conf{XferMethod} = 'smb'.

$Conf{SmbClientPath} = '';
Full path for smbclient. Security caution: normal users should not al-
lowed to write to this file or directory.

smbclient is from the Samba distribution. smbclient is used to actually
extract the incremental or full dump of the share filesystem from the
PC.

This setting only matters if $Conf{XferMethod} = 'smb'.

$Conf{SmbClientFullCmd} = ...
Command to run smbclient for a full dump. This setting only matters if
$Conf{XferMethod} = 'smb'.

The following variables are substituted at run-time:

$smbClientPath same as $Conf{SmbClientPath}
$host host to backup/restore
$hostIP host IP address
$shareName share name
$userName username
$fileList list of files to backup (based on exclude/include)
$I_option optional -I option to smbclient
$X_option exclude option (if $fileList is an exclude list)
$timeStampFile start time for incremental dump

Note: all Cmds are executed directly without a shell, so the prog name
needs to be a full path and you can't include shell syntax like redi-
rection and pipes; put that in a script if you need it.

$Conf{SmbClientIncrCmd} = ...
Command to run smbclient for an incremental dump. This setting only
matters if $Conf{XferMethod} = 'smb'.

Same variable substitutions are applied as $Conf{SmbClientFullCmd}.

Note: all Cmds are executed directly without a shell, so the prog name
needs to be a full path and you can't include shell syntax like redi-
rection and pipes; put that in a script if you need it.

$Conf{SmbClientRestoreCmd} = ...
Command to run smbclient for a restore. This setting only matters if
$Conf{XferMethod} = 'smb'.

Same variable substitutions are applied as $Conf{SmbClientFullCmd}.

If your smb share is read-only then direct restores will fail. You
should set $Conf{SmbClientRestoreCmd} to undef and the corresponding
CGI restore option will be removed.

Note: all Cmds are executed directly without a shell, so the prog name
needs to be a full path and you can't include shell syntax like redi-
rection and pipes; put that in a script if you need it.

Tar Configuration
$Conf{TarShareName} = '/';
Which host directories to backup when using tar transport. This can be
a string or an array of strings if there are multiple directories to
backup per host. Examples:

$Conf{TarShareName} = '/'; # backup everything
$Conf{TarShareName} = '/home'; # only backup /home
$Conf{TarShareName} = ['/home', '/src']; # backup /home and /src

The fact this parameter is called 'TarShareName' is for historical con-
sistency with the Smb transport options. You can use any valid direc-
tory on the client: there is no need for it to correspond to any Smb
share or device mount point.

Note also that you can also use $Conf{BackupFilesOnly} to specify a
specific list of directories to backup. It's more efficient to use
this option instead of $Conf{TarShareName} since a new tar is run for
each entry in $Conf{TarShareName}.

On the other hand, if you add --one-file-system to $Conf{TarClientCmd}
you can backup each file system separately, which makes restoring one
bad file system easier. In this case you would list all of the mount
points here, since you can't get the same result with $Conf{Backup-
FilesOnly}:

$Conf{TarShareName} = ['/', '/var', '/data', '/boot'];

This setting only matters if $Conf{XferMethod} = 'tar'.

$Conf{TarClientCmd} = '$sshPath -q -x -n -l root $host env LC_ALL=C
$tarPath -c -v -f - -C $shareName+ --totals';
Command to run tar on the client. GNU tar is required. You will need
to fill in the correct paths for ssh2 on the local host (server) and
GNU tar on the client. Security caution: normal users should not al-
lowed to write to these executable files or directories.

$Conf{TarClientCmd} is appended with with either $Conf{TarFullArgs} or
$Conf{TarIncrArgs} to create the final command that is run.

See the documentation for more information about setting up ssh2 keys.

If you plan to use NFS then tar just runs locally and ssh2 is not
needed. For example, assuming the client filesystem is mounted below
/mnt/hostName, you could use something like:

$Conf{TarClientCmd} = '$tarPath -c -v -f - -C /mnt/$host/$shareName'
. ' --totals';

In the case of NFS or rsh you need to make sure BackupPC's privileges
are sufficient to read all the files you want to backup. Also, you
will probably want to add "/proc" to $Conf{BackupFilesExclude}.

The following variables are substituted at run-time:

$host hostname
$hostIP host's IP address
$incrDate newer-than date for incremental backups
$shareName share name to backup (ie: top-level directory path)
$fileList specific files to backup or exclude
$tarPath same as $Conf{TarClientPath}
$sshPath same as $Conf{SshPath}

If a variable is followed by a "+" it is shell escaped. This is neces-
sary for the command part of ssh or rsh, since it ends up getting
passed through the shell.

This setting only matters if $Conf{XferMethod} = 'tar'.

Note: all Cmds are executed directly without a shell, so the prog name
needs to be a full path and you can't include shell syntax like redi-
rection and pipes; put that in a script if you need it.

$Conf{TarFullArgs} = '$fileList+';
Extra tar arguments for full backups. Several variables are substi-
tuted at run-time. See $Conf{TarClientCmd} for the list of variable
substitutions.

If you are running tar locally (ie: without rsh or ssh) then remove the
"+" so that the argument is no longer shell escaped.

This setting only matters if $Conf{XferMethod} = 'tar'.

$Conf{TarIncrArgs} = '--newer=$incrDate+ $fileList+';
Extra tar arguments for incr backups. Several variables are substi-
tuted at run-time. See $Conf{TarClientCmd} for the list of variable
substitutions.

Note that GNU tar has several methods for specifying incremental back-
ups, including:

--newer-mtime $incrDate+
This causes a file to be included if the modification time is
later than $incrDate (meaning its contents might have changed).
But changes in the ownership or modes will not qualify the
file to be included in an incremental.

--newer=$incrDate+
This causes the file to be included if any attribute of the
file is later than $incrDate, meaning either attributes or
the modification time. This is the default method. Do
not use --atime-preserve in $Conf{TarClientCmd} above,
otherwise resetting the atime (access time) counts as an
attribute change, meaning the file will always be included
in each new incremental dump.

If you are running tar locally (ie: without rsh or ssh) then remove the
"+" so that the argument is no longer shell escaped.

This setting only matters if $Conf{XferMethod} = 'tar'.

$Conf{TarClientRestoreCmd} = ...
Full command to run tar for restore on the client. GNU tar is re-
quired. This can be the same as $Conf{TarClientCmd}, with tar's -c re-
placed by -x and ssh's -n removed.

See $Conf{TarClientCmd} for full details.

This setting only matters if $Conf{XferMethod} = "tar".

If you want to disable direct restores using tar, you should set
$Conf{TarClientRestoreCmd} to undef and the corresponding CGI restore
option will be removed.

Note: all Cmds are executed directly without a shell, so the prog name
needs to be a full path and you can't include shell syntax like redi-
rection and pipes; put that in a script if you need it.

$Conf{TarClientPath} = '';
Full path for tar on the client. Security caution: normal users should
not allowed to write to this file or directory.

This setting only matters if $Conf{XferMethod} = 'tar'.

Rsync/Rsyncd Configuration
$Conf{RsyncClientPath} = '';
Path to rsync executable on the client. If it is set, it is passed to
to rsync_bpc using the --rsync-path option. You can also add sudo, for
example:

$Conf{RsyncClientPath} = 'sudo /usr/bin/rsync';

For OSX laptop clients, you can use caffeinate to make sure the laptop
stays awake during the backup, eg:

$Conf{RsyncClientPath} = '/usr/bin/sudo /usr/bin/caffeinate -ism /usr/bin/rsync';

This setting only matters if $Conf{XferMethod} = 'rsync'.

$Conf{RsyncBackupPCPath} = "";
Full path to rsync_bpc on the server. Rsync_bpc is the customized ver-
sion of rsync that is used on the server for rsync and rsyncd trans-
fers.

$Conf{RsyncSshArgs} = ['-e', '$sshPath -l root'];
Ssh arguments for rsync to run ssh to connect to the client. Rather
than permit root ssh on the client, it is more secure to just allow ssh
via a low-privileged user, and use sudo in $Conf{RsyncClientPath}.

The setting should only have two entries: "-e" and everything else;
don't add additional array elements.

This setting only matters if $Conf{XferMethod} = 'rsync'.

$Conf{RsyncShareName} = '/';
Share name to backup. For $Conf{XferMethod} = "rsync" this should be a
file system path, eg '/' or '/home'.

For $Conf{XferMethod} = "rsyncd" this should be the name of the module
to backup (ie: the name from /etc/rsynd.conf).

This can also be a list of multiple file system paths or modules. For
example, by adding --one-file-system to $Conf{RsyncArgs} you can backup
each file system separately, which makes restoring one bad file system
easier. In this case you would list all of the mount points:

$Conf{RsyncShareName} = ['/', '/var', '/data', '/boot'];

$Conf{RsyncdClientPort} = 873;
Rsync daemon port on the client, for $Conf{XferMethod} = "rsyncd".

$Conf{RsyncdUserName} = '';
Rsync daemon username on client, for $Conf{XferMethod} = "rsyncd". The
username and password are stored on the client in whatever file the
"secrets file" parameter in rsyncd.conf points to (eg: /etc/rsyncd.se-
crets).

$Conf{RsyncdPasswd} = '';
Rsync daemon username on client, for $Conf{XferMethod} = "rsyncd". The
username and password are stored on the client in whatever file the
"secrets file" parameter in rsyncd.conf points to (eg: /etc/rsyncd.se-
crets).

$Conf{RsyncArgs} = [ ... ];
Arguments to rsync for backup. Do not edit the first set unless you
have a good understanding of rsync options.

$Conf{RsyncArgsExtra} = [];
Additional arguments added to RsyncArgs. This can be used in combina-
tion with $Conf{RsyncArgs} to allow customization of the rsync argu-
ments on a part-client basis. The standard arguments go in $Conf{Rsyn-
cArgs} and $Conf{RsyncArgsExtra} can be set on a per-client basis.

Examples of additional arguments that should work are --exclude/--in-
clude, eg:

$Conf{RsyncArgsExtra} = [
'--exclude', '/proc',
'--exclude', '*.tmp',
'--acls',
'--xattrs',
];

Both $Conf{RsyncArgs} and $Conf{RsyncArgsExtra} are subject to the fol-
lowing variable substitutions:

$client client name being backed up
$host hostname (could be different from client name if
$Conf{ClientNameAlias} is set)
$hostIP IP address of host
$confDir configuration directory path
$shareName share name being backed up

This allows settings of the form:

$Conf{RsyncArgsExtra} = [
'--exclude-from=$confDir/pc/$host.exclude',
];

$Conf{RsyncFullArgsExtra} = ['--checksum'];
Additional arguments for a full rsync or rsyncd backup.

The --checksum argument causes the client to send full-file checksum
for every file (meaning the client reads every file and computes the
checksum, which is sent with the file list). On the server, rsync_bpc
will skip any files that have a matching full-file checksum, and size,
mtime and number of hardlinks. Any file that has different attributes
will be updating using the block rsync algorithm.

In V3, full backups applied the block rsync algorithm to every file,
which is a lot slower but a bit more conservative. To get that behav-
ior, replace --checksum with --ignore-times.

$Conf{RsyncIncrArgsExtra} = [];
Additional arguments for an incremental rsync or rsyncd backup.

$Conf{RsyncRestoreArgs} = [ ... ];
Arguments to rsync for restore. Do not edit the first set unless you
have a thorough understanding of how File::RsyncP works.

If you want to disable direct restores using rsync (eg: is the module
is read-only), you should set $Conf{RsyncRestoreArgs} to undef and the
corresponding CGI restore option will be removed.

$Conf{RsyncRestoreArgs} is subject to the following variable substitu-
tions:

$client client name being backed up
$host hostname (could be different from client name if
$Conf{ClientNameAlias} is set)
$hostIP IP address of host
$confDir configuration directory path

Note: $Conf{RsyncArgsExtra} doesn't apply to $Conf{RsyncRestoreArgs}.

$Conf{RsyncRestoreArgsExtra} = [];
Additional arguments for an rsync or rsyncd restore.

This makes it easy to have per-client arguments.

FTP Configuration
$Conf{FtpShareName} = '';
Which host directories to backup when using FTP. This can be a string
or an array of strings if there are multiple shares per host.

This value must be specified in one of two ways: either as a subdirec-
tory of the 'share root' on the server, or as the absolute path of the
directory.

In the following example, if the directory /home/username is the root
share of the ftp server with the given username, the following two val-
ues will back up the same directory:

$Conf{FtpShareName} = 'www'; # www directory
$Conf{FtpShareName} = '/home/username/www'; # same directory

Path resolution is not supported; i.e.; you may not have an ftp share
path defined as '../otheruser' or '~/games'.

Multiple shares may also be specified, as with other protocols:

$Conf{FtpShareName} = [ 'www',
'bin',
'config' ];

Note also that you can also use $Conf{BackupFilesOnly} to specify a
specific list of directories to backup. It's more efficient to use
this option instead of $Conf{FtpShareName} since a new tar is run for
each entry in $Conf{FtpShareName}.

This setting only matters if $Conf{XferMethod} = 'ftp'.

$Conf{FtpUserName} = '';
FTP username. This is used to log into the server.

This setting is used only if $Conf{XferMethod} = 'ftp'.

$Conf{FtpPasswd} = '';
FTP user password. This is used to log into the server.

This setting is used only if $Conf{XferMethod} = 'ftp'.

$Conf{FtpPassive} = 1;
Whether passive mode is used. The correct setting depends upon whether
local or remote ports are accessible from the other machine, which is
affected by any firewall or routers between the FTP server on the
client and the BackupPC server.

This setting is used only if $Conf{XferMethod} = 'ftp'.

$Conf{FtpBlockSize} = 10240;
Transfer block size. This sets the size of the amounts of data in each
frame. While undefined, this value takes the default value.

This setting is used only if $Conf{XferMethod} = 'ftp'.

$Conf{FtpPort} = 21;
The port of the ftp server. If undefined, 21 is used.

This setting is used only if $Conf{XferMethod} = 'ftp'.

$Conf{FtpTimeout} = 120;
Connection timeout for FTP. When undefined, the default is 120 sec-
onds.

This setting is used only if $Conf{XferMethod} = 'ftp'.

$Conf{FtpFollowSymlinks} = 0;
Behaviour when BackupPC encounters symlinks on the FTP share.

Symlinks cannot be restored via FTP, so the desired behaviour will be
different depending on the setup of the share. The default for this be-
havior is 1. Directory shares with more complicated directory struc-
tures should consider other protocols.

Archive Configuration
$Conf{ArchiveDest} = '/tmp';
Archive Destination

The Destination of the archive e.g. /tmp for file archive or /dev/nst0
for device archive

$Conf{ArchiveComp} = 'gzip';
Archive Compression type

The valid values are:

- 'none': No Compression

- 'gzip': Medium Compression. Recommended.

- 'bzip2': High Compression but takes longer.

$Conf{ArchivePar} = 0;
Archive Parity Files

The amount of Parity data to generate, as a percentage of the archive
size. Uses the command line par2 (par2cmdline) available from
http://parchive.sourceforge.net

Only useful for file dumps.

Set to 0 to disable this feature.

$Conf{ArchiveSplit} = 0;
Archive Size Split

Only for file archives. Splits the output into the specified size *
1,000,000. e.g. to split into 650,000,000 bytes, specify 650 below.

If the value is 0, or if $Conf{ArchiveDest} is an existing file or de-
vice (e.g. a streaming tape drive), this feature is disabled.

$Conf{ArchiveClientCmd} = ...
Archive Command

This is the command that is called to actually run the archive process
for each host. The following variables are substituted at run-time:

$Installdir The installation directory of BackupPC
$tarCreatePath The path to BackupPC_tarCreate
$splitpath The path to the split program
$parpath The path to the par2 program
$host The host to archive
$backupnumber The backup number of the host to archive
$compression The path to the compression program
$compext The extension assigned to the compression type
$splitsize The number of bytes to split archives into
$archiveloc The location to put the archive
$parfile The amount of parity data to create (percentage)

Note: all Cmds are executed directly without a shell, so the prog name
needs to be a full path and you can't include shell syntax like redi-
rection and pipes; put that in a script if you need it.

$Conf{SshPath} = '';
Full path for ssh. Security caution: normal users should not allowed to
write to this file or directory.

$Conf{NmbLookupPath} = '';
Full path for nmblookup. Security caution: normal users should not al-
lowed to write to this file or directory.

nmblookup is from the Samba distribution. nmblookup is used to get the
netbios name, necessary for DHCP hosts.

$Conf{NmbLookupCmd} = '$nmbLookupPath -A $host';
NmbLookup command. Given an IP address, does an nmblookup on that IP
address. The following variables are substituted at run-time:

$nmbLookupPath path to nmblookup ($Conf{NmbLookupPath})
$host IP address

This command is only used for DHCP hosts: given an IP address, this
command should try to find its NetBios name.

Note: all Cmds are executed directly without a shell, so the prog name
needs to be a full path and you can't include shell syntax like redi-
rection and pipes; put that in a script if you need it.

$Conf{NmbLookupFindHostCmd} = '$nmbLookupPath $host';
NmbLookup command. Given a netbios name, finds that host by doing a
NetBios lookup. Several variables are substituted at run-time:

$nmbLookupPath path to nmblookup ($Conf{NmbLookupPath})
$host NetBios name

In some cases you might need to change the broadcast address, for exam-
ple if nmblookup uses 192.168.255.255 by default and you find that
doesn't work, try 192.168.1.255 (or your equivalent class C address)
using the -B option:

$Conf{NmbLookupFindHostCmd} = '$nmbLookupPath -B 192.168.1.255 $host';

If you use a WINS server and your machines don't respond to multicast
NetBios requests you can use this (replace 1.2.3.4 with the IP address
of your WINS server):

$Conf{NmbLookupFindHostCmd} = '$nmbLookupPath -R -U 1.2.3.4 $host';

This is preferred over multicast since it minimizes network traffic.

Experiment manually for your site to see what form of nmblookup command
works.

Note: all Cmds are executed directly without a shell, so the prog name
needs to be a full path and you can't include shell syntax like redi-
rection and pipes; put that in a script if you need it.

$Conf{FixedIPNetBiosNameCheck} = 0;
For fixed IP address hosts, BackupPC_dump can also verify the netbios
name to ensure it matches the hostname. An error is generated if they
do not match. Typically this flag is off. But if you are going to
transition a bunch of machines from fixed host addresses to DHCP, set-
ting this flag is a great way to verify that the machines have their
netbios name set correctly before turning on DHCP.

$Conf{PingPath} = '';
Full path to the ping command. Security caution: normal users should
not be allowed to write to this file or directory.

If you want to disable ping checking, set this to some program that ex-
its with 0 status, eg:

$Conf{PingPath} = '/bin/echo';

$Conf{Ping6Path} = '';
Like PingPath, but for IPv6. Security caution: normal users should not
be allowed to write to this file or directory. In some environments,
this is something like '/usr/bin/ping6'. In modern environments, the
regular ping command can handle both IPv4 and IPv6. In the latter case,
just set it to $Conf{PingPath}

If you want to disable ping checking for IPv6 hosts, set this to some
program that exits with 0 status, eg:

$Conf{Ping6Path} = '/bin/echo';

$Conf{PingCmd} = '$pingPath -c 1 $host';
Ping command. The following variables are substituted at run-time:

$pingPath path to ping ($Conf{PingPath} or $Conf{Ping6Path})
depending on the address type of $host.
$host hostname

Wade Brown reports that on solaris 2.6 and 2.7 ping -s returns the
wrong exit status (0 even on failure). Replace with "ping $host 1",
which gets the correct exit status but we don't get the round-trip
time.

Note: all Cmds are executed directly without a shell, so the prog name
needs to be a full path and you can't include shell syntax like redi-
rection and pipes; put that in a script if you need it.

$Conf{PingMaxMsec} = 20;
Maximum round-trip ping time in milliseconds. This threshold is set to
avoid backing up PCs that are remotely connected through WAN or dialup
connections. The output from ping -s (assuming it is supported on your
system) is used to check the round-trip packet time. On your local LAN
round-trip times should be much less than 20msec. On most WAN or di-
alup connections the round-trip time will be typically more than
20msec. Tune if necessary.

$Conf{CompressLevel} = 3;
Compression level to use on files. 0 means no compression. Compres-
sion levels can be from 1 (least cpu time, slightly worse compression)
to 9 (most cpu time, slightly better compression). The recommended
value is 3. Changing to 5, for example, will take maybe 20% more cpu
time and will get another 2-3% additional compression. See the zlib
documentation for more information about compression levels.

Changing compression on or off after backups have already been done
will require both compressed and uncompressed pool files to be stored.
This will increase the pool storage requirements, at least until all
the old backups expire and are deleted.

It is ok to change the compression value (from one non-zero value to
another non-zero value) after dumps are already done. Since BackupPC
matches pool files by comparing the uncompressed versions, it will
still correctly match new incoming files against existing pool files.
The new compression level will take effect only for new files that are
newly compressed and added to the pool.

If compression was off and you are enabling compression for the first
time you can use the BackupPC_compressPool utility to compress the
pool. This avoids having the pool grow to accommodate both compressed
and uncompressed backups. See the documentation for more information.

$Conf{ClientTimeout} = 72000;
Timeout in seconds when listening for the transport program's (smb-
client, tar etc) stdout. If no output is received during this time,
then it is assumed that something has wedged during a backup, and the
backup is terminated.

Note that stdout buffering combined with huge files being backed up
could cause longish delays in the output from smbclient that Back-
upPC_dump sees, so in some cases you might want to increase this value.

For rsync, this is passed onto rsync_bpc using the --timeout argument,
which is based on any I/O, so you could likely reduce this value.

$Conf{MaxOldPerPCLogFiles} = 12;
Maximum number of log files we keep around in each PC's directory (ie:
pc/$host). These files are aged monthly. A setting of 12 means there
will be at most the files LOG, LOG.0, LOG.1, ... LOG.11 in the pc/$host
directory (ie: about a year's worth). (Except this month's LOG, these
files will have a .z extension if compression is on).

If you decrease this number after BackupPC has been running for a while
you will have to manually remove the older log files.

$Conf{DumpPreUserCmd} = undef;
$Conf{DumpPostUserCmd} = undef;
$Conf{DumpPreShareCmd} = undef;
$Conf{DumpPostShareCmd} = undef;
$Conf{RestorePreUserCmd} = undef;
$Conf{RestorePostUserCmd} = undef;
$Conf{ArchivePreUserCmd} = undef;
$Conf{ArchivePostUserCmd} = undef;
Optional commands to run before and after dumps and restores, and also
before and after each share of a dump.

Stdout from these commands will be written to the Xfer (or Restore) log
file. One example of using these commands would be to shut down and
restart a database server, dump a database to files for backup, or do-
ing a snapshot of a share prior to a backup. Example:

$Conf{DumpPreUserCmd} = '$sshPath -q -x -l root $host /usr/bin/dumpMysql';

The following variable substitutions are made at run time for
$Conf{DumpPreUserCmd}, $Conf{DumpPostUserCmd}, $Conf{DumpPreShareCmd}
and $Conf{DumpPostShareCmd}:

$type type of dump (incr or full)
$xferOK 1 if the dump succeeded, 0 if it didn't
$client client name being backed up
$host hostname (could be different from client name if
$Conf{ClientNameAlias} is set)
$hostIP IP address of host
$user username from the hosts file
$moreUsers list of additional users from the hosts file
$share the first share name (or current share for
$Conf{DumpPreShareCmd} and $Conf{DumpPostShareCmd})
$shares list of all the share names
$XferMethod value of $Conf{XferMethod} (eg: tar, rsync, smb)
$sshPath value of $Conf{SshPath},
$cmdType set to DumpPreUserCmd or DumpPostUserCmd

The following variable substitutions are made at run time for $Conf{Re-
storePreUserCmd} and $Conf{RestorePostUserCmd}:

$client client name being backed up
$xferOK 1 if the restore succeeded, 0 if it didn't
$host hostname (could be different from client name if
$Conf{ClientNameAlias} is set)
$hostIP IP address of host
$user username from the hosts file
$moreUsers list of additional users from the hosts file
$share the first share name
$XferMethod value of $Conf{XferMethod} (eg: tar, rsync, smb)
$sshPath value of $Conf{SshPath},
$type set to "restore"
$bkupSrcHost hostname of the restore source
$bkupSrcShare share name of the restore source
$bkupSrcNum backup number of the restore source
$pathHdrSrc common starting path of restore source
$pathHdrDest common starting path of destination
$fileList list of files being restored
$cmdType set to RestorePreUserCmd or RestorePostUserCmd

The following variable substitutions are made at run time for
$Conf{ArchivePreUserCmd} and $Conf{ArchivePostUserCmd}:

$client client name being backed up
$xferOK 1 if the archive succeeded, 0 if it didn't
$host Name of the archive host
$user username from the hosts file
$share the first share name
$XferMethod value of $Conf{XferMethod} (eg: tar, rsync, smb)
$HostList list of hosts being archived
$BackupList list of backup numbers for the hosts being archived
$archiveloc location where the archive is sent to
$parfile amount of parity data being generated (percentage)
$compression compression program being used (eg: cat, gzip, bzip2)
$compext extension used for compression type (eg: raw, gz, bz2)
$splitsize size of the files that the archive creates
$sshPath value of $Conf{SshPath},
$type set to "archive"
$cmdType set to ArchivePreUserCmd or ArchivePostUserCmd

Note: all Cmds are executed directly without a shell, so the prog name
needs to be a full path and you can't include shell syntax like redi-
rection and pipes; put that in a script if you need it.

$Conf{UserCmdCheckStatus} = 0;
Whether the exit status of each PreUserCmd and PostUserCmd is checked.

If set and the Dump/Restore/Archive Pre/Post UserCmd returns a non-zero
exit status then the dump/restore/archive is aborted. To maintain
backward compatibility (where the exit status in early versions was al-
ways ignored), this flag defaults to 0.

If this flag is set and the Dump/Restore/Archive PreUserCmd fails then
the matching Dump/Restore/Archive PostUserCmd is not executed. If
DumpPreShareCmd returns a non-exit status, then DumpPostShareCmd is not
executed, but the DumpPostUserCmd is still run (since DumpPreUserCmd
must have previously succeeded).

An example of a DumpPreUserCmd that might fail is a script that snap-
shots or dumps a database which fails because of some database error.

$Conf{ClientNameAlias} = undef;
Override the client's hostname. This allows multiple clients to all
refer to the same physical host. This should only be set in the per-PC
config file and is only used by BackupPC at the last moment prior to
checking the host is alive, and generating the command used to backup #
that machine (ie: the value of $Conf{ClientNameAlias} is invisible
everywhere else in BackupPC). The setting can be a hostname or IP ad-
dress, eg:

$Conf{ClientNameAlias} = 'realHostName';
$Conf{ClientNameAlias} = '192.1.1.15';

which will cause the relevant smb/tar/rsync backup/restore commands to
be directed to realHostName or the IP address, not the client name.

It can also be an array, to allow checking (in order) of several host
names or IP addresses that refer to the same host. For example, if
your client has a wired and wireless connection you could set:

$Conf{ClientNameAlias} = ['hostname-lan', 'hostname-wifi'];

If hostname-lan is alive, it will be used for the backup/restore. If
not, the next name (hostname-wifi) is tested.

Note: this setting doesn't work for hosts with DHCP set to 1.

$Conf{ClientComment} = undef;
A user-settable comment string that is displayed in this host's status.
The value is otherwise ignored by BackupPC.

Email reminders, status and messages
$Conf{SendmailPath} = '';
Full path to the sendmail command. Security caution: normal users
should not allowed to write to this file or directory.

$Conf{EMailNotifyMinDays} = 2.5;
Minimum period between consecutive emails to a single user. This tries
to keep annoying email to users to a reasonable level. Email checks
are done nightly, so this number is effectively rounded up (ie: 2.5
means a user will never receive email more than once every 3 days).

$Conf{EMailFromUserName} = '';
Name to use as the "from" name for email. Depending upon your mail
handler this is either a plain name (eg: "admin") or a fully-qualified
name (eg: "admin@mydomain.com").

$Conf{EMailAdminUserName} = '';
Destination address to an administrative user who will receive a
nightly email with warnings and errors. If there are no warnings or
errors then no email will be sent. Depending upon your mail handler
this is either a plain name (eg: "admin") or a fully-qualified name
(eg: "admin@mydomain.com").

$Conf{EMailAdminSubject} = '';
Subject for admin emails. If empty, defaults to pre-4.2.2 values.

$Conf{EMailUserDestDomain} = '';
Destination domain name for email sent to users. By default this is
empty, meaning email is sent to plain, unqualified addresses. Other-
wise, set it to the destination domain, eg:

$Cong{EMailUserDestDomain} = '@mydomain.com';

With this setting user email will be set to 'user@mydomain.com'.

$Conf{EMailNoBackupEverSubj} = undef;
$Conf{EMailNoBackupEverMesg} = undef;
This subject and message is sent to a user if their PC has never been
backed up.

These values are language-dependent. The default versions can be found
in the language file (eg: lib/BackupPC/Lang/en.pm). If you need to
change the message, copy it here and edit it, eg:

$Conf{EMailNoBackupEverMesg} = <<'EOF';
To: $user$domain
cc:
Subject: $subj

Dear $userName,

This is a site-specific email message.
EOF

$Conf{EMailNotifyOldBackupDays} = 7.0;
How old the most recent backup has to be before notifying user. When
there have been no backups in this number of days the user is sent an
email.

$Conf{EMailNoBackupRecentSubj} = undef;
$Conf{EMailNoBackupRecentMesg} = undef;
This subject and message is sent to a user if their PC has not recently
been backed up (ie: more than $Conf{EMailNotifyOldBackupDays} days
ago).

These values are language-dependent. The default versions can be found
in the language file (eg: lib/BackupPC/Lang/en.pm). If you need to
change the message, copy it here and edit it, eg:

$Conf{EMailNoBackupRecentMesg} = <<'EOF';
To: $user$domain
cc:
Subject: $subj

Dear $userName,

This is a site-specific email message.
EOF

$Conf{EMailNotifyOldOutlookDays} = 5.0;
How old the most recent backup of Outlook files has to be before noti-
fying user.

$Conf{EMailOutlookBackupSubj} = undef;
$Conf{EMailOutlookBackupMesg} = undef;
This subject and message is sent to a user if their Outlook files have
not recently been backed up (ie: more than $Conf{EMailNotifyOldOutlook-
Days} days ago).

These values are language-dependent. The default versions can be found
in the language file (eg: lib/BackupPC/Lang/en.pm). If you need to
change the message, copy it here and edit it, eg:

$Conf{EMailOutlookBackupMesg} = <<'EOF';
To: $user$domain
cc:
Subject: $subj

Dear $userName,

This is a site-specific email message.
EOF

$Conf{EMailHeaders} = <<EOF;
Additional email headers. This sets to charset to utf8.

CGI user interface configuration settings
$Conf{CgiAdminUserGroup} = '';
$Conf{CgiAdminUsers} = '';
Normal users can only access information specific to their host. They
can start/stop/browse/restore backups.

Administrative users have full access to all hosts, plus overall status
and log information.

The administrative users are the union of the list of unix/linux
groups, separated by spaces, in $Conf{CgiAdminUserGroup} and the list
of users, separated by spaces, in $Conf{CgiAdminUsers}. If you don't
want a list of groups or users set the corresponding configuration set-
ting to undef or an empty string.

If you want every user to have admin privileges (careful!), set
$Conf{CgiAdminUsers} = '*'.

Examples:

$Conf{CgiAdminUserGroup} = 'admin wheel';
$Conf{CgiAdminUsers} = 'craig celia';
--> administrative users are the union of groups admin and wheel, plus
craig and celia.

$Conf{CgiAdminUserGroup} = '';
$Conf{CgiAdminUsers} = 'craig celia';
--> administrative users are only craig and celia'.

$Conf{SCGIServerPort} = -1;
TCP port number of the SCGI server. A negative value disables the SCGI
server. Set to any available unprivileged TCP port number, eg: 10268.
Apache needs the mod_scgi module installed, and you will need to set
the same port number in the Apache configuration. Here are some typical
settings you'll need in Apache's httpd.conf:

$Conf{CgiURL} = '';
Full URL of the BackupPC_Admin CGI script, or the configured path for
SCGI. Used for links in email messages.

$Conf{RrdToolPath} = '';
Full path to the rrdtool command. If available, graphs of pool usage
will be generated. If empty, then the graphs will be skipped.

Security caution: normal users should not allowed to write to this file
or directory.

$Conf{Language} = 'en';
Language to use. See lib/BackupPC/Lang for the list of supported lan-
guages, which include English (en), French (fr), Spanish (es), German
(de), Italian (it), Dutch (nl), Polish (pl), Portuguese Brazilian
(pt_br) and Chinese (zh_CN).

Currently the Language setting applies to the CGI interface and email
messages sent to users. Log files and other text are still in English.

$Conf{CgiUserHomePageCheck} = '';
$Conf{CgiUserUrlCreate} = 'mailto:%s';
User names that are rendered by the CGI interface can be turned into
links into their home page or other information about the user. To set
this up you need to create two sprintf() strings, that each contain a
single '%s' that will be replaced by the user name. The default is a
mailto: link.

$Conf{CgiUserHomePageCheck} should be an absolute file path that is
used to check (via "-f") that the user has a valid home page. Set this
to undef or an empty string to turn off this check.

$Conf{CgiUserUrlCreate} should be a full URL that points to the user's
home page. Set this to undef or an empty string to turn off generation
of URLs for usernames.

Example:

$Conf{CgiUserHomePageCheck} = '/var/www/html/users/%s.html';
$Conf{CgiUserUrlCreate} = 'http://myhost/users/%s.html';
--> if /var/www/html/users/craig.html exists, then 'craig' will
be rendered as a link to http://myhost/users/craig.html.

$Conf{CgiDateFormatMMDD} = 2;
Date display format for CGI interface. A value of 1 uses US-style
dates (MM/DD), a value of 2 uses full YYYY-MM-DD format, and zero for
international dates (DD/MM).

$Conf{CgiNavBarAdminAllHosts} = 1;
If set, the complete list of hosts appears in the left navigation bar
pull-down for administrators. Otherwise, just the hosts for which the
user is listed in the host file (as either the user or in moreUsers)
are displayed.

$Conf{CgiSearchBoxEnable} = 1;
Enable/disable the search box in the navigation bar.

$Conf{CgiNavBarLinks} = [ ... ];
Additional navigation bar links. These appear for both regular users
and administrators. This is a list of hashes giving the link (URL) and
the text (name) for the link. Specifying lname instead of name uses
the language specific string (ie: $Lang->{lname}) instead of just lit-
erally displaying name.

$Conf{CgiStatusHilightColor} = { ...
Highlight colors based on status that are used in the PC summary page.

$Conf{CgiHeaders} = '<meta http-equiv="pragma" content="no-cache">';
Additional CGI header text.

$Conf{CgiImageDir} = '';
Directory where images are stored. This directory should be below
Apache's DocumentRoot. This value isn't used by BackupPC but is used
by configure.pl when you upgrade BackupPC.

Example:

$Conf{CgiImageDir} = '/var/www/htdocs/BackupPC';

$Conf{CgiExt2ContentType} = {};
Additional mappings of filename extensions to Content-Type for individ-
ual file restore. See $Ext2ContentType in BackupPC_Admin for the de-
fault setting. You can add additional settings here, or override any
default settings. Example:

$Conf{CgiExt2ContentType} = {
'pl' => 'text/plain',
};

$Conf{CgiImageDirURL} = '';
URL (without the leading http://host) for BackupPC's image directory.
The CGI script uses this value to serve up image files.

Example:

$Conf{CgiImageDirURL} = '/BackupPC';

$Conf{CgiCSSFile} = 'BackupPC_stnd.css';
CSS stylesheet "skin" for the CGI interface. It is stored in the
$Conf{CgiImageDir} directory and accessed via the $Conf{CgiImageDirURL}
URL.

For BackupPC v3 and v2 the prior css versions are available as Back-
upPC_retro_v3.css and BackupPC_retro_v2.css

$Conf{CgiUserDeleteBackupEnable} = 0;
Whether the user is allowed to delete backups. If set to a positive
value, the user will have a delete button for each backup on any host
they have permission to access. If set to 0, only administrators have
access to the backup delete feature. If set to a negative value, even
admins will not be able to use the delete feature.

$Conf{CgiUserConfigEditEnable} = 1;
Whether the user is allowed to edit their per-PC config.

$Conf{CgiUserConfigEdit} = { ...
Which per-host config variables a non-admin user is allowed to edit.
Admin users can edit all per-host config variables, even if disabled in
this list.

SECURITY WARNING: Do not let users edit any of the Cmd config vari-
ables! That's because a user could set a Cmd to a shell script of
their choice and it will be run as the BackupPC user. That script
could do all sorts of bad things.

Version Numbers
BackupPC uses a X.Y.Z version numbering system. The first digit is for ma-
jor new releases, the middle digit is for significant feature releases and
improvements (most of the releases have been in this category).

Author
Craig Barratt <cbarratt@users.sourceforge.net>

See <https://backuppc.github.io/backuppc/BackupPC.html>.

Credits
Ryan Kucera contributed the directory navigation code and images for
v1.5.0. He contributed the first skeleton of BackupPC_restore. He also
added a significant revision to the CGI interface, including CSS tags, in
v2.1.0, and designed the BackupPC logo.

Xavier Nicollet, with additions from Guillaume Filion, added the interna-
tionalization (i18n) support to the CGI interface for v2.0.0. Xavier pro-
vided the French translation fr.pm, with additions from Guillaume.

Guillaume Filion wrote BackupPC_zipCreate and added the CGI support for zip
download, in addition to some CGI cleanup, for v1.5.0. Guillaume continues
to support fr.pm updates for each new version.

Josh Marshall implemented the Archive feature in v2.1.0.

Ludovic Drolez supports the BackupPC Debian package.

Javier Gonzalez provided the Spanish translation, es.pm for v2.0.0.

Manfred Herrmann provided the German translation, de.pm for v2.0.0. Man-
fred continues to support de.pm updates for each new version, together with
some help from Ralph PaAAgang.

Lorenzo Cappelletti provided the Italian translation, it.pm for v2.1.0.
Giuseppe Iuculano and Vittorio Macchi updated it for 3.0.0.

Lieven Bridts provided the Dutch translation, nl.pm, for v2.1.0, with some
tweaks from Guus Houtzager, and updates for 3.0.0.

Reginaldo Ferreira provided the Portuguese Brazilian translation pt_br.pm
for v2.2.0.

Rich Duzenbury provided the RSS feed option to the CGI interface.

Jono Woodhouse from CapeSoft Software (www.capesoft.com) provided a new CSS
skin for 3.0.0 with several layout improvements. Sean Cameron (also from
CapeSoft) designed new and more compact file icons for 3.0.0.

Youlin Feng provided the Chinese translation for 3.1.0.

Karol 'Semper' Stelmaczonek provided the Polish translation for 3.1.0.

Jeremy Tietsort provided the host summary table sorting feature for 3.1.0.

Paul Mantz contributed the ftp Xfer method for 3.2.0.

Petr Pokorny provided the Czech translation for 3.2.1.

Rikiya Yamamoto provided the Japanese translation for 3.3.0.

Yakim provided the Ukrainian translation for 3.3.0.

Sergei Butakov provided the Russian translation for 3.3.0.

Alexander Moisseev provided the rrdtool graphing code in 4.0.0 and has pro-
vided many fixes and improvements in 3.x and 4.x.

Many people have provided user support on the mail lists, reported bugs,
made useful suggestions, and helped with testing; see the ChangeLog and the
mailing lists.

Your name could appear here in the next version!

License
This program is free software: you can redistribute it and/or modify it un-
der the terms of the GNU General Public License as published by the Free
Software Foundation, either version 3 of the License, or (at your option)
any later version.

This program is distributed in the hope that it will be useful, but WITHOUT
ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FIT-
NESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more
details.

You should have received a copy of the GNU General Public License along
with this program. If not, see <http://www.gnu.org/licenses/>.

4.4.0 2020-06-20 BackupPC(1)

Want to link to this manual page? Use this URL:
<https://man.freebsd.org/cgi/man.cgi?query=backuppc&sektion=1&manpath=FreeBSD+Ports+15.1.quarterly>

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