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SNAPSHOT(8) System Manager's Manual SNAPSHOT(8) NAME snapshot -- UFS/ZFS snapshot management utility SYNOPSIS snapshot [options] [command] [arguments] DESCRIPTION The snapshot command is a convenience frontend to mount(8) and mdconfig(8) for the management of UFS/ZFS snapshots. It is also the underlying tool used in the periodic snapshot scheduler periodic-snapshot(8) and the mount- ing/unmouning command in the amd(8) map /etc/amd.map.snap. It provides the making, expiring, visiting, mounting and unmounting of filesystem snap- shots. The following global options are available: -v Display verbose messages showing the essential system commands in- volved in the operation. -h Display a short usage help message and exit. -d subdir Set the subdirectory on filesystems under which snapshots are placed. The default is the conventional .snap subdirectory dump(8) uses, too. The following commands are available: snapshot list [fs ...] List all existing snapshots on all filesystems or just the particu- lar filesystems specified by fs. The output shows both actual disk-space user usage ("User", "User%") and the disk-space snapshot usage ("Snap", "Snap%"). snapshot make [-g max-generations] fs:tag[.generation] Makes a new snapshot generation named tag on filesystem fs, located in the file fs/subdir/tag.generation. If the generation part is omitted, generation 0 is used. All older generations (with numbers greater than generation) are rotated and all obsoleted generations (with numbers greater or equal to max-generations) are removed. Keep in mind that a maximum total number of 20 snapshots can be created on a UFS filesystem only. A max-generations number of 0 effectively deletes all snapshots on filesystem fs of name tag only. snapshot mount [-o mount-option] fs:tag[.generation] dir Mounts the fs snapshot tag.generation (or tag.0 if generation is omitted) under dir by attaching the snapshot file to the next free md(4) device and mounting this device read-only onto the target di- rectory. If options -o are specified, they are passed-through to mount(8). snapshot umount dir Unmounts a snapshot by umounting the md(4) device from dir, deat- taching the snapshot file from the corresponding md(4) device and deleting the device. snapshot visit fs:tag[.generation] This is just a convenience command which mounts the specified filesystem on /mnt, temporarily changes to /mnt, starts an interac- tive shell there for inspecting the snapshot content, and upon exit from the shell immediately unmounts the snapshot again. EXAMPLE The following sample session illustrates the making, rotation, mounting, unmounting and removal of snapshots: root# snapshot list /var Filesystem User User% Snap Snap% Snapshot root# snapshot make -g4 /var:test root# snapshot list /var Filesystem User User% Snap Snap% Snapshot /var 1172MB 14.8% 4MB 0.1% test.0 root# snapshot make -g4 /var:test root# snapshot list /var Filesystem User User% Snap Snap% Snapshot /var 1176MB 14.8% 4MB 0.1% test.0 /var 1176MB 14.8% 4MB 0.1% test.1 root# snapshot make -g4 /var:test root# snapshot list /var Filesystem User User% Snap Snap% Snapshot /var 1181MB 14.9% 4MB 0.1% test.0 /var 1181MB 14.9% 4MB 0.1% test.1 /var 1181MB 14.9% 4MB 0.1% test.2 root# snapshot make -g4 /var:test root# snapshot list /var Filesystem User User% Snap Snap% Snapshot /var 1186MB 15.0% 4MB 0.1% test.0 /var 1186MB 15.0% 4MB 0.1% test.1 /var 1186MB 15.0% 4MB 0.1% test.2 /var 1186MB 15.0% 4MB 0.1% test.3 root# snapshot make -g4 /var:test root# snapshot list /var Filesystem User User% Snap Snap% Snapshot /var 1186MB 15.0% 4MB 0.1% test.0 /var 1186MB 15.0% 4MB 0.1% test.1 /var 1186MB 15.0% 4MB 0.1% test.2 /var 1186MB 15.0% 4MB 0.1% test.3 root# snapshot mount /var:test.2 /mnt root# ls /mnt account cron heimdal mail opkg spool at db lib msgs preserve tmp backups empty log named run yp root# snapshot umount /mnt root# snapshot make -g0 /var:test root# snapshot list /var Filesystem User User% Snap Snap% Snapshot root# _ By using an amd(8) map /usr/local/etc/amd.map.snap containing /defaults type:=program * mount:="/usr/local/sbin/snapshot snapshot mount /${key} ${fs}";\ unmount:="/usr/local/sbin/snapshot snapshot umount ${fs}" and a /etc/rc.conf configuration of amd_enable="YES" amd_flags="-a /.am -c 1800 -w 60 -l syslog /snap /usr/local/etc/amd.map.snap" even non-privileged users can access arbitrary snapshots fs:tag[generation] by just accessing /snap/fs:tag[generation]. For instance, if a snapshot hourly.2 exists on filesystem /var one can then access an old state of file /var/tmp/foo.txt by simply accessing the path /snap/var:hourly.2/tmp/foo.txt. SEE ALSO mount(8), mdconfig(8), md(4), periodic-snapshot(8), http://peo- ple.freebsd.org/~rse/snapshot/. HISTORY The snapshot utility first appeared in FreeBSD. AUTHORS Ralf S. Engelschall <rse@FreeBSD.org> FreeBSD ports 15.quarterly September 3, 2004 SNAPSHOT(8)
NAME | SYNOPSIS | DESCRIPTION | EXAMPLE | SEE ALSO | HISTORY | AUTHORS
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