Copyright (c) 1980 Regents of the University of California.
All rights reserved. The Berkeley software License Agreement
specifies the terms and conditions for redistribution.

@(#)fsck.8 5.1 (Berkeley) 04/27/85

C 4 \\$1\l'|0\(ul' .. fsck - file system consistency check and interactive repair /etc/fsck -p [ filesystem ... ]

/etc/fsck [ -b block# ] [ -y ] [ -n ] [ filesystem ] ...

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 fstab causes a disk to not be checked; similarly partitions 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 .ns Link counts in inodes too large .ns Missing blocks in the free list .ns Blocks in the free list also in files .ns 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 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 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.

The following flags are interpreted by fsck.

6 -b Use the block specified immediately after the flag as the super block for the file system. Block 32 is always an alternate super block.

6 -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.

6 -n Assume a no response to all questions asked by fsck; do not open the file system for writing.

If no filesystems are given to fsck then a default list of file systems is read from the file /etc/fstab .

Inconsistencies checked are as follows:

6 1. Blocks claimed by more than one inode or the free list.

.ns

6 2. Blocks claimed by an inode or the free list outside the range of the file system.

.ns

6 3. Incorrect link counts.

.ns

6 4. Size checks:

.ns

Directory size not of proper format.

.ns

6 5. Bad inode format.

.ns

6 6. Blocks not accounted for anywhere.

.ns

6 7. Directory checks:

.ns

File pointing to unallocated inode.

Inode number out of range.

.ns

6 8. Super Block checks:

.ns

More blocks for inodes than there are in the file system.

.ns

6 9. Bad free block list format.

.ns

6 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.

.ns

21 /etc/fstab contains default list of file systems to check.

The diagnostics produced by fsck are intended to be self-explanatory. fstab(5), fs(5), newfs(8), mkfs(8), crash(8V), reboot(8) 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.