sbin/fsck/fsck.8

.\"	$NetBSD: fsck.8,v 1.19 1999/03/10 00:08:33 erh Exp $
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.\" Copyright (c) 1996 Christos Zoulas.  All rights reserved.
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.Dd March 5, 2019
.Dt FSCK 8
.Os
.Sh NAME
.Nm fsck
.Nd file system consistency check and interactive repair
.Sh SYNOPSIS
.Nm
.Op Fl Cdfnpvy
.Op Fl B | F
.Op Fl T Ar fstype : Ns Ar fsoptions
.Op Fl t Ar fstype
.Op Fl c Ar fstab
.Oo Ar special | node Oc ...
.Sh DESCRIPTION
The
.Nm
utility invokes file system-specific programs to check
the special devices listed in the
.Xr fstab 5
file or in the command line for consistency.
.Pp
It is normally used in the script
.Pa /etc/rc
during automatic reboot.
Traditionally,
.Nm
is invoked before the file systems are mounted
and all checks are done to completion at that time.
If background checking is available,
.Nm
is invoked twice.
It is first invoked at the traditional time,
before the file systems are mounted, with the
.Fl F
flag to do checking on all the file systems
that cannot do background checking.
It is then invoked a second time,
after the system has completed going multiuser, with the
.Fl B
flag to do checking on all the file systems
that can do background checking.
Unlike the foreground checking,
the background checking is started asynchronously
so that other system activity can proceed
even on the file systems that are being checked.
.Pp
If no file systems are specified,
.Nm
reads the table
.Pa /etc/fstab
to determine which file systems to check.
Only partitions in
.Pa /etc/fstab
that are mounted
.Dq rw ,
.Dq rq
or
.Dq ro
and that have non-zero pass number are checked.
File systems with pass number 1 (normally just the root file system)
are always checked one at a time.
.Pp
If not in preen mode, the remaining entries are checked in order of
increasing pass number one at a time.
This is needed when interaction with
.Nm
is required.
.Pp
In preen mode, after pass 1 completes, all remaining file systems are checked,
in pass number order running one process per disk drive in parallel for each
pass number in increasing order.
.Pp
In other words: In preen mode all pass 1 partitions are checked sequentially.
Next all pass 2 partitions are checked in parallel, one process per disk drive.
Next all pass 3 partitions are checked in parallel, one process per disk drive.
etc.
.Pp
The disk drive containing each file system is inferred from the shortest prefix
of the device name that ends in a digit; the remaining characters are assumed
to be the partition and slice designators.
.Pp
If the
.Fl t
or
.Fl T
flags are not specified,
.Nm
will attempt to determine the file system type and call the
appropriate file system check utility.
Failure to detect the file system type will cause
.Nm
to fail with a message that the partition has an unknown file system type.
.Pp
The options are as follows:
.Bl -tag -width indent
.It Fl C
Check if the
.Dq clean
flag is set in the superblock and skip file system checks if file system was
properly dismounted and marked clean.
.It Fl c Ar fstab
Specify the
.Pa fstab
file to use.
.It Fl d
Debugging mode.
Just print the commands without executing them.
Available
only if
.Nm
is compiled to support it.
.It Fl f
Force checking of file systems.
Running
.Dq Li fsck -f
ignores the journal and does a full
consistency check of the disk so will find and fix the errors about which the
journal is unaware.
.It Fl n
Causes
.Nm
to assume no as the answer to all operator questions, except "CONTINUE?".
.It Fl p
Enter preen mode.
In preen mode, only a restricted class of innocuous
file system inconsistencies will be corrected.
If unexpected inconsistencies caused by hardware or
software failures are encountered, the check program
will exit with a failure.
See the manual pages for the individual check programs
for a list of the sorts of failures that they correct
when running in preen mode.
.It Fl F
Run in foreground mode.
The check program for each file system is invoked with the
.Fl F
flag to determine whether it wishes to run as part of
the boot up sequence,
or if it is able to do its job in background after the
system is up and running.
A non-zero exit code indicates that it wants to run in foreground
and the check program is invoked.
A zero exit code indicates that it is able to run later in background
and just a deferred message is printed.
.It Fl B
Run in background mode.
The check program for each file system is invoked with the
.Fl F
flag to determine whether it wishes to run as part of
the boot up sequence,
or if it is able to do its job in background after the
system is up and running.
A non-zero exit code indicates that it wanted to run in foreground
which is assumed to have been done, so the file system is skipped.
A zero exit code indicates that it is able to run in background
so the check program is invoked with the
.Fl B
flag to indicate that a check on the active file system should be done.
When running in background mode,
only one file system at a time will be checked.
Note that background
.Nm
is limited to checking for only the most commonly occurring
file system abnormalities.
Under certain circumstances,
some errors can escape background
.Nm .
It is recommended that you perform foreground
.Nm
on your systems periodically and whenever you encounter
file-system\-related panics.
.It Fl t Ar fstype
Invoke
.Nm
only for the comma separated list of file system types.
If the
list starts with
.Dq no
then invoke
.Nm
for the file system types that are not specified in the list.
.It Fl v
Print the commands before executing them.
.It Fl y
Causes
.Nm
to assume yes
as the answer to all operator questions.
.It Fl T Ar fstype : Ns Ar fsoptions
List of comma separated file system specific options for the specified
file system type, in the same format as
.Xr mount 8 .
.El
.Sh FILES
.Bl -tag -width /etc/fstab -compact
.It Pa /etc/fstab
file system table
.El
.Sh SEE ALSO
.Xr fstab 5 ,
.Xr fsck_ffs 8 ,
.Xr fsck_msdosfs 8 ,
.Xr mount 8
.Sh HISTORY
A
.Nm
utility appeared in
.Bx 4.0 .
It was reimplemented as a filesystem independent wrapper in
.Nx 1.3
and first appeared in
.Fx 5.0 .
The original filesystem specific utility became
.Xr fsck_ffs 8
at this point.