fsck(8) CLIX fsck(8)
NAME
fsck, dfsck - Checks and repairs file systems
SYNOPSIS
/etc/fsck [-y] [-n] [-sX] [-SX] [-t file] [-q] [-D] [-f] [-b] [special]
/etc/dfsck [options1] special1 ... - [options2] special2 ...
FLAGS
-y Assumes a ``yes'' response to all questions asked by the fsck
command.
-n Assumes a ``no'' response to all questions asked by the fsck
command, but does not open the file system for writing.
-sX Ignores the actual free list and unconditionally reconstructs a
new one by rewriting the superblock 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 quiescent
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 flag allows for creating an optimal free-list
organization. If X is not given, the values used when the file
system was created are used. The format of X is cylinder-
size:gap-size.
-SX Conditionally reconstructs the free list. This flag 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 the fsck
command. This flag is useful for forcing free list
reorganization on uncontaminated file systems.
-t file If the fsck command cannot obtain enough memory to keep its
tables, it uses a scratch file. If the -t flag is specified,
the file named in the next argument is used as the scratch file,
if needed. Without the -t flag, the fsck command will prompt
the user for the name of the scratch file. The file chosen
should not be on the file system being checked, and if it is not
a special file or did not already exist, it is removed when the
fsck command completes its processing.
-q Quiet mode for the fsck command. In this mode, the command does
not display size-check messages. Unreferenced FIFOs will
silently be removed. If the fsck command requires it, counts in
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the superblock will be automatically fixed and the free list
salvaged.
-D When using this flag, directories are checked for bad blocks.
This flag is useful after system crashes.
-f Fast check mode. This flag causes the command to check blocks,
sizes and check the free list. The free list will be
reconstructed if it is necessary.
-b Reboot flag. If the file system being checked is the root file
system and modifications have been made, then the user must
either remount the root file system or reboot the system. A
remount is done only if there was minor damage.
DESCRIPTION
Fsck Command
The fsck command audits and interactively repairs inconsistent conditions
for file systems. If the file system is found to be consistent, the
number of files, blocks used, and blocks free are reported. If the file
system is inconsistent the user is prompted for concurrence before each
correction is attempted. It should be noted that most corrective actions
will result in some loss of data. The amount and severity of data loss
may be determined from the diagnostic output. The default action for each
correction is to wait for the user to respond yes or no. If the user does
not have write permission, the fsck command defaults to a -n action.
The fsck command audits an fs type file system as the default file system
and also acts as a front-end driver for other file system types. if the
file system is not the default type, it executes the fstyp command, forms
a pathname from the output, and executes the audit program so formed. for
example, if the fstyp command reports the file system to be of type ffs,
the fsck command will cause the ffsfsck command to execute.
If no special files are specified, the fsck command will read a list of
default file systems from the file /etc/checklist. 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. The following size checks are carried out:
a. Incorrect number of blocks.
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b. Directory size not 16-byte aligned.
5. Bad inode format.
6. Blocks not accounted for anywhere.
7. The following directory checks are made:
a. File pointing to unallocated inode.
b. inode number out of range.
8. The following superblock checks are made:
a. More than 65536 inodes.
b. 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.
If orphaned files and directories (allocated but unreferenced) contain
data, with the user's concurrence, they are reconnected by placing them in
the file system's lost+found directory. The user will be notified whether
the file or directory is empty. Empty files or directories are removed,
as long as the -n flag is not specified. The fsck command will force the
reconnection of nonempty directories. The name assigned is the inode
number. The only restriction is that the directory lost+found must
preexist in the root directory of the file system being checked and must
have empty slots in which entries can be made. This is accomplished by
running the mklost+found command in the root directory of the file system
when the file system is created.
Checking the raw device is always faster and should be used with
everything but the root file system.
dfsck Command
The dfsck command allows two file system checks on two different drives
simultaneously. The options1 and options2 are used to pass options to
fsck for the two sets of file systems. A - is used as the separator
between the file system groups.
The dfsck command permits a user to interact with two fsck commands at
once. To aid in this, the dfsck command displays the file system name for
each message to the user. When answering a question from dfsck, the user
must prefix the response with a 1 or a 2 (indicating that the answer
refers to the first or second file system group).
FILES
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fsck(8) CLIX fsck(8)
/etc/checklist Contains default list of file systems to check
CAUTIONS
The inode numbers for . and .. in each directory are not checked for
validity.
DIAGNOSTICS
In addition to the diagnostic messages displayed below, other messages may
be displayed while checking the file system and are normal to the
operation of the fsck command.
Can't open checklist file: file
The /etc/checklist file is missing.
Cannot exec fsck_command
The fsck command appropriate to the file system type could not be
invoked. This may indicate an unusual file system type.
ROOT INODE UNALLOCATED. TERMINATING.
The inode for the root directory does not exist. The fsck command
cannot repair this error.
EXIT VALUES
The following exit values are returned for the fsck command:
0 Check Completed.
8 fsck error (bad options, out of memory, couldn't open file)
4 Directory pathname too long.
RELATED INFORMATION
Commands: ffsfsck(8), mklost+found(8), fstyp(8), ncheck(8), crash(8)
Functions: uadmin(2)
Files: checklist(4), fs(4)
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