FSCK(8) GENIX Programmer's Manual FSCK(8)
NAME
fsck - file system consistency check and interactive repair
SYNOPSIS
/etc/fsck -p [ filesystem ... ]
/etc/fsck [ -y ] [ -n ] [ -sX ] [ -SX ] [ -t filename ] [ filesystem
] ...
DESCRIPTION
The first form of fsck preens a standard set of filesystems or the
specified file systems. It is normally used in the script /etc/rc
during automatic reboot. In this case fsck reads the table
/etc/fstab to determine which file systems to check. It uses the
information there to inspect groups of disks in parallel taking max-
imum advantage of i/o overlap to check the file systems as quickly
as possible. Normally, the root file system will be checked on pass
1, other ``root'' (``a'' partition) file systems on pass 2, other
small file systems on separate passes (e.g. the ``d'' file systems
on pass 3 and the ``e'' file systems on pass 4), and finally the
large user file systems on the last pass, e.g. pass 5. A pass
number of 0 in fstab causes a disk to not be checked; similarly par-
titions which are not shown as to be mounted ``rw'' or ``ro'' are
not checked.
The system takes care that only a restricted class of innocuous
inconsistencies can happen unless hardware or software failures
intervene. These are limited to the following:
Unreferenced inodes
Link counts in inodes too large
Missing blocks in the free list
Blocks in the free list also in files
Counts in the super-block wrong
These are the only inconsistencies which fsck with the -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, fsck will print the number of files on that file system
and the number of used and free blocks.
Without the -p option, fsck audits and interactively repairs incon-
sistent conditions for file systems. If the file system is incon-
sistent the operator is prompted for concurrence before each correc-
tion is attempted. It should be noted that a number of the correc-
tive actions which are not fixable under the -p option will result
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FSCK(8) GENIX Programmer's Manual FSCK(8)
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 yes or
no. If the operator does not have write permission fsck will
default to a -n action.
Fsck has more consistency checks than its predecessors check,
dcheck, fcheck, and icheck combined.
The following flags are interpreted by fsck.
-y Assume a yes response to all questions asked by fsck; this
should be used with great caution as this is a free license to
continue after essentially unlimited trouble has been encoun-
tered.
-n Assume a no response to all questions asked by fsck; do not
open the file system for writing.
-sX Ignore the actual free list and (unconditionally) reconstruct
a new one by rewriting the super-block of the file system. The
file system should be unmounted while this is done; if this is
not possible, care should be taken that the system is quies-
cent and that it is rebooted immediately afterwards. This
precaution is necessary so that the old, bad, in-core copy of
the superblock will not continue to be used, or written on the
file system.
The -sX option allows for creating an optimal free-list organ-
ization. The following forms of X are supported for the fol-
lowing devices:
-s3 (RP03)
-s4 (RP04, RP05, RP06)
-sBlocks-per-cylinder:Blocks-to-skip (for anything else)
If X is not given, the values used when the filesystem was
created are used. If these values were not specified, then
the value 400:9 is used.
-SX Conditionally reconstruct the free list. This option is like
-sX above except that the free list is rebuilt only if there
were no discrepancies discovered in the file system. Using -S
will force a no response to all questions asked by fsck. This
option is useful for forcing free list reorganization on
uncontaminated file systems.
-t If fsck cannot obtain enough memory to keep its tables, it
uses a scratch file. If the -t option is specified, the file
named in the next argument is used as the scratch file, if
needed. Without the -t flag, fsck will prompt the operator for
the name of the scratch file. The file chosen should not be on
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the filesystem being checked, and if it is not a special file
or did not already exist, it is removed when fsck completes.
If no filesystems are given to fsck then a default list of file sys-
tems is read from the file /etc/fstab.
Inconsistencies checked are as follows:
1. Blocks claimed by more than one inode or the free list.
2. Blocks claimed by an inode or the free list outside the range
of the file system.
3. Incorrect link counts.
4. Size checks:
Directory size not 16-byte aligned.
5. Bad inode format.
6. Blocks not accounted for anywhere.
7. Directory checks:
File pointing to unallocated inode.
Inode number out of range.
8. Super Block checks:
More than 65536 inodes.
More blocks for inodes than there are in the file sys-
tem.
9. Bad free block list format.
10. Total free block and/or free inode count incorrect.
Orphaned files and directories (allocated but unreferenced) are,
with the operator's concurrence, reconnected by placing them in the
lost+found directory. The name assigned is the inode number. The
only restriction is that the directory lost+found must preexist in
the root of the filesystem being checked and must have empty slots
in which entries can be made. This is accomplished by making
lost+found, copying a number of files to the directory, and then
removing them (before fsck is executed).
Checking the raw device is almost always faster.
FILES
/etc/fstab contains default list of file systems to check.
DIAGNOSTICS
The diagnostics produced by fsck are intended to be self-
explanatory.
SEE ALSO
fstab(5), fs(5), crash(8), reboot(8)
BUGS
Inode numbers for . and .. in each directory should be checked for
validity.
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FSCK(8) GENIX Programmer's Manual FSCK(8)
-g and -b options from check should be available in fsck.
There should be some way to start a fsck -p at pass n.
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