sbin/fsck_ffs/fsck_ffs.8

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.Dd November 17, 2023
.Dt FSCK_FFS 8
.Os
.Sh NAME
.Nm fsck_ffs ,
.Nm fsck_ufs
.Nd file system consistency check and interactive repair
.Sh SYNOPSIS
.Nm
.Op Fl BCdEFfnpRrSyZz
.Op Fl b Ar block
.Op Fl c Ar level
.Op Fl m Ar mode
.Ar filesystem
.Ar ...
.Sh DESCRIPTION
The specified disk partitions and/or file systems are checked.
In "preen" or "check clean" mode the clean flag of each file system's
superblock is examined and only those file systems that are not marked clean
are checked.
File systems are marked clean when they are unmounted,
when they have been mounted read-only, or when
.Nm
runs on them successfully.
If the
.Fl f
option is specified, the file systems
will be checked regardless of the state of their clean flag.
.Pp
The kernel takes care that only a restricted class of innocuous file system
inconsistencies can happen unless hardware or software failures intervene.
These are limited to the following:
.Pp
.Bl -item -compact -offset indent
.It
Unreferenced inodes
.It
Link counts in inodes too large
.It
Missing blocks in the free map
.It
Blocks in the free map also in files
.It
Counts in the super-block wrong
.El
.Pp
These are the only inconsistencies that
.Nm
with the
.Fl p
option will correct; if it encounters other inconsistencies, it exits
with an abnormal return status and an automatic reboot will then fail.
For each corrected inconsistency one or more lines will be printed
identifying the file system on which the correction will take place,
and the nature of the correction.
After successfully correcting a file system,
.Nm
will print the number of files on that file system,
the number of used and free blocks,
and the percentage of fragmentation.
.Pp
If sent a
.Dv QUIT
signal,
.Nm
will finish the file system checks, then exit with an abnormal
return status that causes an automatic reboot to fail.
This is useful when you want to finish the file system checks during an
automatic reboot,
but do not want the machine to come up multiuser after the checks complete.
.Pp
If
.Nm
receives a
.Dv SIGINFO
(see the
.Dq status
argument for
.Xr stty 1 )
signal, a line will be written to the standard output indicating
the name of the device currently being checked, the current phase
number and phase-specific progress information.
.Pp
Without the
.Fl p
option,
.Nm
audits and interactively repairs inconsistent conditions for file systems.
If the file system is inconsistent the operator is prompted for concurrence
before each correction is attempted.
It should be noted that some of the corrective actions which are not
correctable under the
.Fl p
option will result in some loss of data.
The amount and severity of data lost may be determined from the diagnostic
output.
The default action for each consistency correction
is to wait for the operator to respond
.Li yes
or
.Li no .
If the operator does not have write permission on the file system
.Nm
will default to a
.Fl n
action.
.Pp
The following flags are interpreted by
.Nm :
.Bl -tag -width indent
.It Fl B
A check is done on the specified and possibly active file system.
The set of corrections that can be done is limited to those done
when running in preen mode (see the
.Fl p
flag).
If unexpected errors are found,
the file system is marked as needing a foreground check and
.Nm
exits without attempting any further cleaning.
.It Fl b
Use the block specified immediately after the flag as
the super block for the file system.
An alternate super block is usually located at block 32 for UFS1,
and block 192 for UFS2.
.Pp
See the
.Fl N
flag of
.Xr newfs 8 .
.It Fl C
Check if file system was dismounted cleanly.
If so, skip file system checks (like "preen").
However, if the file system was not cleanly dismounted, do full checks,
as if
.Nm
was invoked without
.Fl C .
.It Fl c
Convert the file system to the specified level.
Note that the level of a file system can only be raised.
There are currently four levels defined:
.Bl -tag -width indent
.It 0
The file system is in the old (static table) format.
.It 1
The file system is in the new (dynamic table) format.
.It 2
The file system supports 32-bit uid's and gid's,
short symbolic links are stored in the inode,
and directories have an added field showing the file type.
.It 3
If maxcontig is greater than one,
build the free segment maps to aid in finding contiguous sets of blocks.
If maxcontig is equal to one, delete any existing segment maps.
.El
.Pp
In interactive mode,
.Nm
will list the conversion to be made
and ask whether the conversion should be done.
If a negative answer is given,
no further operations are done on the file system.
In preen mode,
the conversion is listed and done if
possible without user interaction.
Conversion in preen mode is best used when all the file systems
are being converted at once.
The format of a file system can be determined from the
first line of output from
.Xr dumpfs 8 .
.Pp
This option implies the
.Fl f
flag.
.It Fl d
Enable debugging messages.
.It Fl E
Clear unallocated blocks, notifying the underlying device that they
are not used and that their contents may be discarded.
This is useful for filesystems which have been mounted on systems
without TRIM support, or with TRIM support disabled, as well as
filesystems which have been copied from one device to another.
.Pp
See the
.Fl E
and
.Fl t
flags of
.Xr newfs 8 ,
and
the
.Fl t
flag of
.Xr tunefs 8 .
.It Fl F
Determine whether the file system needs to be cleaned immediately
in foreground, or if its cleaning can be deferred to background.
To be eligible for background cleaning it must have been running
with soft updates, not have been marked as needing a foreground check,
and be mounted and writable when the background check is to be done.
If these conditions are met, then
.Nm
exits with a zero exit status.
Otherwise it exits with a non-zero exit status.
If the file system is clean,
it will exit with a non-zero exit status so that the clean status
of the file system can be verified and reported during the foreground
checks.
Note that when invoked with the
.Fl F
flag, no cleanups are done.
The only thing that
.Nm
does is to determine whether a foreground or background
check is needed and exit with an appropriate status code.
.It Fl f
Force
.Nm
to check
.Sq clean
file systems when preening.
.It Fl m
Use the mode specified in octal immediately after the flag as the
permission bits to use when creating the
.Pa lost+found
directory rather than the default 1777.
In particular, systems that do not wish to have lost files accessible
by all users on the system should use a more restrictive
set of permissions such as 700.
.It Fl n
Assume a no response to all questions asked by
.Nm
except for
.Ql CONTINUE? ,
which is assumed to be affirmative;
do not open the file system for writing.
.It Fl p
Preen file systems (see above).
.It Fl R
Instruct fsck_ffs to restart itself if it encounters certain errors that
warrant another run.
It will limit itself to a maximum of 10 restarts in a given run in order
to avoid an endless loop with extremely corrupted filesystems.
.It Fl r
Free up excess unused inodes.
Decreasing the number of preallocated inodes reduces the
running time of future runs of
.Nm
and frees up space that can allocated to files.
The
.Fl r
option is ignored when running in preen mode.
.It Fl S
Surrender on error.
With this flag enabled, a hard error returned on disk i/o will cause
.Nm
to abort instead of continuing on and possibly tripping over more i/o errors.
.It Fl y
Assume a yes response to all questions asked by
.Nm ;
this should be used with great caution as this is a free license
to continue after essentially unlimited trouble has been encountered.
.It Fl Z
Similar to
.Fl E ,
but overwrites unused blocks with zeroes.
If both
.Fl E
and
.Fl Z
are specified, blocks are first zeroed and then erased.
.It Fl z
Clear unused directory space.
The cleared space includes deleted file names and name padding.
.El
.Pp
Inconsistencies checked are as follows:
.Pp
.Bl -enum -compact
.It
Blocks claimed by more than one inode or the free map.
.It
Blocks claimed by an inode outside the range of the file system.
.It
Incorrect link counts.
.It
Size checks:
.Bl -item -offset indent -compact
.It
Directory size not a multiple of DIRBLKSIZ.
.It
Partially truncated file.
.El
.It
Bad inode format.
.It
Blocks not accounted for anywhere.
.It
Directory checks:
.Bl -item -offset indent -compact
.It
File pointing to unallocated inode.
.It
Inode number out of range.
.It
Directories with unallocated blocks (holes).
.It
Dot or dot-dot not the first two entries of a directory
or having the wrong inode number.
.El
.It
Super Block checks:
.Bl -item -offset indent -compact
.It
More blocks for inodes than there are in the file system.
.It
Bad free block map format.
.It
Total free block and/or free inode count incorrect.
.El
.El
.Pp
Orphaned files and directories (allocated but unreferenced) are,
with the operator's concurrence, reconnected by
placing them in the
.Pa lost+found
directory.
The name assigned is the inode number.
If the
.Pa lost+found
directory does not exist, it is created.
If there is insufficient space its size is increased.
.Pp
The full foreground
.Nm
checks for many more problems that may occur after an
unrecoverable disk write error.
Thus, it is recommended that you perform foreground
.Nm
on your systems periodically and whenever you encounter
unrecoverable disk write errors or file-system\-related panics.
.Sh FILES
.Bl -tag -width /etc/fstab -compact
.It Pa /etc/fstab
contains default list of file systems to check.
.El
.Sh EXIT STATUS
.Ex -std
.Pp
Specific non-zero exit status values used are:
.Bl -tag -width indent
.It 1
Usage error (missing or invalid command arguments).
.It 2
The
.Fl p
option was used and a
.Dv SIGQUIT
was received, indicating that the system should be returned to single
user mode after the file system check.
.It 3
The file system superblock cannot be read.
This could indicate that the file system device does not exist or is not yet
ready.
.It 4
A mounted file system was modified; the system should be rebooted.
.It 5
The
.Fl B
option was used and soft updates are not enabled on the file system.
.It 6
The
.Fl B
option was used and the kernel lacks needed support.
.It 7
The
.Fl F
option was used and the file system is clean.
.It 8
General error exit.
.It 16
The file system could not be completely repaired.
The file system may be able to be repaired by running
.Nm
on the file system again.
.El
.Sh DIAGNOSTICS
The diagnostics produced by
.Nm
are fully enumerated and explained in Appendix A of
.Rs
.%T "Fsck \- The UNIX File System Check Program"
.Re
.Sh SEE ALSO
.Xr fs 5 ,
.Xr fstab 5 ,
.Xr ffs 7 ,
.Xr fsck 8 ,
.Xr fsdb 8 ,
.Xr newfs 8 ,
.Xr reboot 8
.Sh HISTORY
A
.Nm fsck
utility appeared in
.Bx 4.0 .
It became
.Nm
in
.Fx 5.0
with the introduction of the filesystem independent wrapper as
.Nm fsck .