FSCK(8) COMMAND REFERENCE FSCK(8)
NAME
fsck - file system consistency check and interactive repair
SYNOPSIS
/etc/fsck -p [ filesystem ... ]
/etc/fsck [ -b block# ] [ -n ] [ -y ] [ 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 maximum 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 /etc/fstab causes a disk to not be checked;
similarly partitions which are not marked 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 started by /etc/rc 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
inconsistent conditions for file systems. If the file
Printed 10/17/86 1
FSCK(8) COMMAND REFERENCE FSCK(8)
system is inconsistent the operator is prompted for
concurrence before each correction is attempted. It should
be noted that a number of the corrective actions which are
not fixable under the -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 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.
OPTIONS
The following flags are interpreted by fsck.
-b Use the block specified immediately after the flag as
the super block for the file system. Here, block means
a 512-byte block. Block 32 (in 512-byte blocks) is
always an alternate super block.
-n Assume a no response to all questions asked by fsck; do
not open the file system for writing.
-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 encountered.
If no filesystem argument is given to fsck then a default
list of file systems 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 of proper format.
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 blocks for inodes than there are in the
file system.
9. Bad free block list format.
10. Total free block and/or free inode count incorrect.
Printed 10/17/86 2
FSCK(8) COMMAND REFERENCE FSCK(8)
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).
Fsck must be run as super-user.
FILES
/etc/fstab contains default list of file
systems to check
DIAGNOSTICS
The diagnostics produced by fsck are intended to be self-
explanatory.
RETURN VALUE
[0] Everything worked as expected.
[4] Fsck ran normally, except that the root file system was
modified. /etc/rc usually reboots the system if it sees
this return value.
[8] A fatal error occurred. The diagnostic message provided
will give more information.
[12]
An internal inconsistency was found.
CAVEATS
Inode numbers for . and .. in each directory should be
checked for validity.
There should be some way to start a fsck -p at pass n.
SEE ALSO
fstab(5), fs(5), mkfs(8), newfs(8), reboot(8).
Printed 10/17/86 3
%%index%%
na:72,95;
sy:167,365;
de:532,2356;3032,899;
op:3931,1771;5846,687;
fi:6533,160;
di:6693,184;
rv:6877,507;
ca:7384,257;
se:7641,168;
%%index%%000000000165