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DISKCHECKD(8)		     System Manager's Manual		   DISKCHECKD(8)

NAME
     diskcheckd -- daemon to check for disk read errors

SYNOPSIS
     diskcheckd [-d] [-f conf_file] [-o save_file]

DESCRIPTION
     diskcheckd  is  a daemon which runs in the background, reading entire disks
     to find any read errors on those disks.  The disks which should be scanned,
     and the rates at which they should be scanned, must  be  specified  in  the
     configuration file, which is /usr/local/etc/diskcheckd.conf by default.

     Any blank lines or lines starting with a `#' character in this file are ig-
     nored.   Each  non-comment line of this file must be in one of two formats.
     The first format  is  `!xx',  and	specifies  that  device  names	matching
     /dev/xx* should not be included in expansion of wildcards (see below).  The
     second  format consists of four white space separated fields, which are the
     full pathname of the disk device, the size of this disk, the  frequency  in
     days  at  which to check this disk, and the rate in kilobytes per second at
     which to check this disk.

     Either the frequency or the rate should be specified,  not  both,	since  a
     specified	frequency will be internally converted to whatever rate will re-
     sult in the disk being scanned at (approximately) that frequency.	The size
     of the disk should not be specified if the rate  is  specified,  since  the
     size is used only to convert a specified frequency into a rate.

     If  the disk is specified as "*", then diskcheckd will apply the given set-
     tings to all disks in the system,	obtained  using  the  kern.disks  sysctl
     variable.	 If the size is specified as "*" (recommended), then the size of
     the disk will be automatically determined from the disklabel, if  possible.
     Fields which are not specified should contain a single "*" character.

     Note that diskcheckd always reads data from the disk in 64KB blocks, so the
     rate  you	specify  may not be the exact rate at which the disk is actually
     checked.  Similarly, if you specify the  third  field  (days  for	complete
     scan)  it	is unlikely that a complete scan will actually take exactly this
     many days.

     To run diskcheckd automatically at boot time, the	diskcheckd_enable  vari-
     able in rc.conf(5) should be set to "YES".

     When  diskcheckd  receives a SIGTERM or SIGINT signal, it saves its current
     state information to a file, so that after a reboot diskcheckd  can  resume
     reading  from where it left off, rather than starting from the beginning of
     the disk again.  The information saved to this file consists of the  device
     filename and the current offset into that device.

     diskcheckd can be instructed to reload the configuration file by sending it
     a SIGHUP signal.

     diskcheckd accepts the following command line options:

     -d 	 If  this  flag  is specified, diskcheckd will not fork into the
		 background and detach from its controlling terminal to become a
		 daemon, and it will duplicate its system log  messages  on  its
		 standard error output.

		 This flag is primarily used for debugging, and may be specified
		 more than once.  Additional instances will result in additional
		 debugging messages on standard error; these added messages will
		 not be written to the system log.

     -f 	 Specify  the  configuration file to use, instead of the default
		 /usr/local/etc/diskcheckd.conf.

     -o 	 Specify the file to save disk offsets to, instead  of	the  de-
		 fault /var/db/diskcheckd.offsets.

PROGRESS REPORTING
     After every 5 minutes or so of sleep time between reads (not including time
     spent waiting for the reads themselves to complete), diskcheckd will update
     its  command  parameter  space  to show its progress in scanning each disk.
     This report can be viewed using ps(1).

FILES
     /usr/local/etc/diskcheckd.conf
				 Default configuration file.
     /var/db/diskcheckd.offsets  Default location of saved offsets.

EXAMPLES
     To check all of /dev/ad0 for errors once every two weeks, use this entry in
     diskcheckd.conf:

	   /dev/ad0	   *	   14	   *

     To check the first SCSI disk for errors at approximately  64KB/s,	use  the
     following entry:

	   /dev/da0	   *	   *	   64

     To check all disks once every four weeks:

	   *	   *	   28	   *

DIAGNOSTICS
     If any errors occur, they will be written to syslogd(8).

HISTORY
     diskcheckd first appeared in FreeBSD 5.0.

AUTHORS
     diskcheckd   and	this   manual	page   were  written  by  Ben  Smithurst
     <ben@FreeBSD.org>, with input  from  Poul-Henning	Kamp  <phk@FreeBSD.org>.
     The  geom-aware version of the sector->partition translation code was added
     by Perry Hutchison <perryh@pluto.rain.com>, based on a mechanism  suggested
     by Warner Losh <imp@bsdimp.com>.

BUGS
     diskcheckd Too much of the code assumes all disks have 512 byte sectors.

     There  are  two  versions	of the code that attempts to identify and report
     which slice and/or partition contain a detected error.  The older	version,
     used  when the DIOCGDINFO ioctl is available (i.e. prior to FreeBSD 11.0 ),
     does not understand either GPT partitions or dedicated  BSD  disks  (having
     the BSD disklabel in place of an MBR).

FreeBSD ports 15.quarterly	  July 4, 2001			   DISKCHECKD(8)
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