fsck(8) 						      System Manager's Manual							   fsck(8)

NAME

       fsck, ufs_fsck - Check and repair UFS file systems

SYNOPSIS

       /usr/sbin/fsck [fs_options] [filesystem...]

DESCRIPTION

       The  fsck  command is a front-end program for the ufs_fsck program, which checks and repairs UFS file systems.  Do not use this command for
       AdvFS file systems:  instead, see advfs(4).

       The fsck program has more consistency checks than its check, dcheck, fcheck, and icheck predecessors combined.

       You must be root to use this command.

       If you do not specify a file system in the command line, the fsck command checks the file systems in the /etc/fstab file.

       With one exception, the fsck command cannot be used on an active file system. The command checks to determine whether the partition  to	be
       checked,  or  an  overlapping partition, is in use.  The exceptional case occurs when you run the command on an active root file system and
       specify the -f flag.  Use this flag with caution, because it can cause the data on the running system (the in-memory data) to become unsyn-
       chronized from the file system data (the on-disk data).

       The  fsck  program  interactively repairs inconsistent file system conditions.  If the file system is found to be consistent, the number of
       files, blocks used, and free blocks are reported.  If the file  system  is  inconsistent,  you  are  prompted  before  each  correction	is
       attempted.   For  each  corrected inconsistency, one or more lines are displayed, identifying the file system on which the correction takes
       place and the type of correction.  After successfully correcting a file system, the fsck program displays the number of files on that  file
       system, the number of used and free blocks, and the percentage of fragmentation.

       The default behavior of the fsck program is to interactively check the following UFS file system inconsistencies:

       Blocks claimed by more than one inode or the free map

       Blocks claimed by an inode outside the range of the file system

       Incorrect link counts

       Size checks: directory size not of proper format; partially truncated file

       Bad inode format

       Blocks not accounted for anywhere

       Directory  checks:  file  pointing  to unallocated inode; inode number out of range; . (dot) or .. (dot dot) not the first two entries of a
       directory or having the wrong inode number

       Super Block checks: more blocks for inodes than there are in the file system

       Bad free block map format

       Total free block and/or free inode count incorrect

       If you use the -p flag, the fsck program noninteractively attempts to correct specific file system inconsistencies.   The  corrections  are
       made only if they can be done safely.  The fsck program can noninteractively correct the following file system inconsistencies:

       Unreferenced inodes

       Link counts in inodes that are too large

       Missing blocks in the free map

       Blocks in the free map that are also in files

       Wrong counts in the super-block.

       If fsck encounters any other inconsistencies, it exits with an abnormal return status and a subsequent reboot will fail.

       The system makes sure that only a restricted class of innocuous inconsistencies can occur unless hardware or software failures intervene.

       Note  that  some  of  the corrective actions can result in a loss of data.  The amount and severity of data lost can be determined from the
       diagnostic output.

       At system boot, fsck -p runs automatically and reads the /etc/fstab file to determine which file systems to check.   Only  partitions  that
       are  mounted  rw  or  ro and have a non-zero pass (1 or more) number are checked.  File systems that have a pass number 1 (usually only the
       root file system) are checked one at a time.  When pass 1 completes, the remaining pass	numbers  are  processed  with  one  parallel  fsck
       process running per disk drive in the same pass.

       The  per  disk  drive  logic is based on the /dev/disk/dsk0a syntax where different partition letters are treated as being on the same disk
       drive.  Partitions layered on top of an LSM device may not follow this naming convention.  Where LSM is used, you can use unique pass  num-
       bers in the /etc/fstab file to sequence the fsck checks.

       If  a  QUIT  signal  is	sent, fsck finishes the file system checks and then exits with an abnormal return status that causes the automatic
       reboot to fail.	This is useful if 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.

       If  the	fsck  default  program fails (terminates with a non-zero value), fsck terminates with the exit value.  This ensures that the auto-
       reboot dependencies, such as those commonly used in the run command script, continue to function.

       If orphaned files or directories (allocated but unreferenced) are found, you are asked if you want to reconnect the files  and  directories
       that are not empty by putting them in the lost+found directory.	The program indicates whether the file or directory is empty or not empty.
       The fsck program reconnects directories that are not empty and assigns the inode number for the name.  If the lost+found directory does not
       exist,  it  is created, and if it has insufficient space, the size is increased. Empty files and directories are removed unless you specify
       the -n flag.

FLAGS

       The following flags are interpreted by fsck: Uses the specified block number as the super block for the file system.  Block 32  is  usually
       an alternate super block.  Converts UFS Version 4 back to UFS Version 3. When you use the -B option on a UFS Version 4 file system, it will
       be marked as a Version 3 file system if there are no files or directories with more than 32767 hardlinks or 32765 subdirectories.   If  the
       file  system  is in the old (static table) format, converts it to the new (dynamic table) format.  If the file system is in the new format,
       this flag converts it to the old format, provided that the old format can support the file system configuration.  In interactive mode, fsck
       lists  the direction of the conversion and asks if the conversion should be done. If you answer "no," no further operations are done on the
       file system.  If the -p flag is specified, the direction of the conversion is listed and the conversion is performed without user  interac-
       tion  if possible.  The -p flag should be used if all the file systems are being converted simultaneously.  The format of a file system can
       be determined from the first line of output from the dumpfs command.  Forces fsck to check the root file system, even when the file  system
       is  mounted  as writable.  Use this flag with caution, because running fsck on a mounted root file system can cause its files to become out
       of synchronization with running system data.  If the problem occurs, the  fsck program displays a message recommending you reboot the  sys-
       tem.   Limits  the number of parallel checks to the number specified.  By default, the limit is the number of disks running one process per
       disk. If a smaller limit is given, the disks are checked using a round robin-type schedule, one file system at a time.  Uses the mode spec-
       ified  in  octal  as the permission bits to use when creating the lost+found directory rather than the default 777.  In particular, systems
       that do not want to have lost files accessible by all users on the system should use a more restrictive set of permissions,  such  as  700.
       Answers	"no"  to  all the prompts except for the ``CONTINUE?'' prompt.	The flag does not write to the lost+found file in the file system.
       If you do not have write permission on the file system, fsck defaults to the behavior of the -n flag.  Causes fsck to unconditionally check
       the  file  system  even	if  the file system's clean byte is set.  That is, a file system is checked even if it has been unmounted cleanly.
       Noninteractively corrects the following file system inconsistencies: unreferenced inodes, link counts in inodes that are too large, missing
       blocks in the free map, blocks in the free map that are also in files, and wrong counts in the super-block.  Causes more extensive messages
       to be displayed during the file system checks (verbose mode).  Answers "yes" to all the prompts.  This flag should  be  used  with  caution
       because the integrity of the file system data can be corrupted by answering "yes" to all the prompts.

ERRORS

       The following message indicates that the system is avoiding a potential panic by skipping the file system check:

       /dev/disk/dsk2g: skipping filesystem already mounted (read-write) on '/usr'

       The following message indicates that the file system is mounted:

       /dev/disk/dsk2g on /usr: Device busy

       The following message indicates that the partition you are checking is open:

       ERROR: /dev/rdisk/dsk3a or an overlapping partition is open
       fsck cannot be run on an active filesystem

EXAMPLES

       The  following is an example of an /etc/fstab file that is used in the examples in this section: /dev/disk/dsk2a     /		ufs rw 1 1
       /dev/disk/dsk0g	   /usr ufs rw 1 2 /dev/disk/dsk2b     swap1	 ufs sw 0 2  /dev/disk/dsk0b	  /public   ufs  sw  0	2  /dev/disk/dsk2g
       /var ufs rw 1 2 /dev/disk/dsk3c	   /usr/users	  ufs rw 1 2

       The following command checks all the file systems in the /etc/fstab file but makes no corrections: # fsck -n

       The  following example checks a file system found in the /etc/fstab file and checks a file system that is not found in the /etc/fstab file:
       # fsck  /dev/rdisk/dsk3c  /dev/rdisk/dsk1a

       The following command noninteractively checks the file systems in the /etc/fstab file: # fsck -p

FILES

       Specifies the command path Specifies the command path Contains the default list of file systems to check

RELATED INFORMATION

       Commands:  newfs(8) delim off

																	   fsck(8)