Add diskcheck-daemon.

With a small disk being 20GB these days, chances are pretty good that
an ailing sector will not be read while still being recoverable by
the drive.

Diskcheck daemon will read disks in the background at a low rate and
that way give the diskdrive a chance to detect and correct soft read
errors before they become hard errors.

Idea by:	phk
Written by:     ben

1 files changed, 186 insertions, 0 deletions

diff --git a/usr.sbin/diskcheckd/diskcheckd.8 b/usr.sbin/diskcheckd/diskcheckd.8
new file mode 100644
index 0000000..fb9a124
--- /dev/null
+++ b/usr.sbin/diskcheckd/diskcheckd.8
@@ -0,0 +1,186 @@
+.\" Copyright (c) 2000, 2001 Ben Smithurst <ben@FreeBSD.org>
+.\" All rights reserved.
+.\"
+.\" Redistribution and use in source and binary forms, with or without
+.\" modification, are permitted provided that the following conditions
+.\" are met:
+.\" 1. Redistributions of source code must retain the above copyright
+.\"    notice, this list of conditions and the following disclaimer.
+.\" 2. Redistributions in binary form must reproduce the above copyright
+.\"    notice, this list of conditions and the following disclaimer in the
+.\"    documentation and/or other materials provided with the distribution.
+.\"
+.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+.\" ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+.\" SUCH DAMAGE.
+.\"
+.\" $FreeBSD$
+.\"
+.Dd December 30, 2000
+.Dt DISKCHECKD 8
+.Os FreeBSD
+.Sh NAME
+.Nm diskcheckd
+.Nd daemon to check for disk read errors
+.Sh SYNOPSIS
+.Nm
+.Op Fl d
+.Op Fl f Ar conf_file
+.Op Fl o Ar save_file
+.Sh DESCRIPTION
+.Nm
+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
+.Pa /etc/diskcheckd.conf
+by default.
+.Pp
+Any blank lines or lines starting with a
+.Ql #
+character in this file are ignored.
+Each non-comment line of this file should contain four white space separated
+fields,
+which are the full pathname of the disk device,
+the size of that disk,
+the frequency in days at which to check that disk,
+and the rate in kilobytes per second at which to check this disk.
+Naturally,
+it would be contradictory to specify both the frequency and the rate,
+so only one of these should be specified.
+Additionally,
+the size of the disk should not be specified if the rate is specified,
+as this information is unnecessary.
+.Pp
+If the disk is specified as
+.Dq * ,
+then
+.Nm
+will apply the given settings to all disks in the system,
+obtained using the
+.Va kern.disks
+sysctl variable.
+If the size is specified as
+.Dq *
+(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
+.Dq *
+character.
+.Pp
+Note that any rate specified will be rounded to the nearest power of 2,
+and will be forced into the range 512 bytes to 128 kilobytes,
+inclusive.
+Any rate calculated from the frequency and size information will be rounded
+in the same way,
+so if you specify the third field (days for complete scan) it is unlikely
+that a complete scan will actually take exactly this many days.
+.Pp
+To run
+.Nm
+automatically at boot time,
+the
+.Ar diskcheckd_enable
+variable in
+.Xr rc.conf 5
+should be set to
+.Dq YES .
+.Pp
+When
+.Nm
+receives a
+.Dv SIGTERM
+or
+.Dv SIGINT
+signal,
+it saves its current state information to a file,
+so that after a reboot
+.Nm
+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.
+.Pp
+.Nm
+can be instructed to reload the configuration file by sending it a
+.Dv SIGHUP
+signal.
+.Pp
+.Nm
+accepts the following command line options:
+.Pp
+.Bl -tag -width Fl
+.It Fl d
+If this flag is specified,
+.Nm
+will not fork into the background and detach from its controlling terminal
+to become a daemon.
+This flag is primarily used for debugging.
+.It Fl f
+Specify the configuration file to use,
+instead of the default
+.Pa /etc/diskcheckd.conf .
+.It Fl o
+Specify the file to save disk offsets to,
+instead of the default
+.Pa /var/db/diskcheckd.offsets .
+.El
+.Sh FILES
+.Bl -tag -width /var/db/diskcheckd.offsets -compact
+.It Pa /etc/diskcheckd.conf
+Default configuration file.
+.It Pa /var/db/diskcheckd.offsets
+Default location of saved offsets.
+.El
+.Sh EXAMPLES
+To check all of
+.Pa /dev/ad0
+for errors once every two weeks,
+use this entry in
+.Pa diskcheckd.conf :
+.Pp
+.Bd -literal -offset indent
+/dev/ad0	*	14	*
+.Ed
+.Pp
+To check the first SCSI disk for errors at approximately 64KB/s,
+use the following entry:
+.Pp
+.Bd -literal -offset indent
+/dev/da0	*	*	64
+.Ed
+.Pp
+To check all disks once every four weeks:
+.Pp
+.Bd -literal -offset indent
+*	*	28	*
+.Ed
+.Sh DIAGNOSTICS
+If any errors occur,
+they will be written to
+.Xr syslogd 8 .
+.Sh HISTORY
+.Nm
+first appeared in
+.Fx 5.0 .
+.Sh AUTHORS
+.Nm
+and this manual page were written by
+.An Ben Smithurst Aq ben@FreeBSD.org ,
+with input from
+.An Poul-Henning Kamp Aq phk@FreeBSD.org .
+.Sh BUGS
+.Nm
+assumes all disks have 512 byte sectors.