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FSCK_EXT2FS(8)              System Manager's Manual             FSCK_EXT2FS(8)

NAME
     fsck_ext2fs - ext2 File System consistency check and interactive repair

SYNOPSIS
     fsck_ext2fs [-dfnpUy] [-b block#] [-c level] [-m mode] filesystem ...

DESCRIPTION
     fsck_ext2fs performs interactive filesystem consistency checks and repair
     for each of the filesystems specified on the command line.  It is
     normally invoked from fsck(8).

     The kernel takes care that only a restricted class of innocuous
     filesystem 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 map
     Blocks in the free map also in files
     Counts in the super-block wrong

     These are the only inconsistencies that fsck_ext2fs in "preen" mode (with
     the -p option) will correct; if it encounters other inconsistencies, it
     exits with an abnormal return status.  For each corrected inconsistency
     one or more lines will be printed identifying the filesystem on which the
     correction will take place, and the nature of the correction.  After
     successfully correcting a filesystem, fsck_ext2fs will print the number
     of files on that filesystem and the number of used and free blocks.

     If sent a QUIT signal, fsck_ext2fs will finish the filesystem checks,
     then exit with an abnormal return status.

     Without the -p option, fsck_ext2fs audits and interactively repairs
     inconsistent conditions for filesystems.  If the filesystem is
     inconsistent the operator is prompted for concurrence before each
     correction is attempted.  It should be noted that some of the corrective
     actions which are not correctable 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 on the filesystem fsck_ext2fs
     will default to a -n action.

     The following flags are interpreted by fsck_ext2fs.

     -b      Use the block specified immediately after the flag as the super
             block for the filesystem.  Block 8193 is usually an alternate
             super block.

     -d      Print debugging output.

     -f      Force checking of file systems.  Normally, if a file system is
             cleanly unmounted, the kernel will set a "clean flag" in the file
             system superblock, and fsck_ext2fs will not check the file
             system.  This option forces fsck_ext2fs to check the file system,
             regardless of the state of the clean flag.

     -m      Use the mode specified in octal immediately after the flag as the
             permission bits to use when creating the lost+found directory
             rather than the default 1777.  In particular, systems that do not
             wish to have lost files accessible by all users on the system
             should use a more restrictive set of permissions such as 700.

     -n      Assume a no response to all questions asked by fsck_ext2fs except
             for `CONTINUE?', which is assumed to be affirmative; do not open
             the filesystem for writing.

     -p      Specify "preen" mode, described above.

     -U      Resolve numeric userids to usernames.

     -y      Assume a yes response to all questions asked by fsck_ext2fs; this
             should be used with great caution as this is a free license to
             continue after essentially unlimited trouble has been
             encountered.

     Inconsistencies checked are as follows:
           1.   Blocks claimed by more than one inode or the free map.
           2.   Blocks claimed by an inode outside the range of the
                filesystem.
           3.   Incorrect link counts.
           4.   Size checks:
                      Directory size not a multiple of filesystem block size.
                      Partially truncated file.
           5.   Bad inode format.
           6.   Blocks not accounted for anywhere.
           7.   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.
           8.   Super Block checks:
                      More blocks for inodes than there are in the filesystem.
                      Bad free block map format.
                      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.  If the lost+found
     directory does not exist, it is created.  If there is insufficient space
     its size is increased.

     Because of inconsistencies between the block device and the buffer cache,
     the raw device should always be used.

DIAGNOSTICS
     The diagnostics produced by fsck_ext2fs are fully enumerated and
     explained in Appendix A of Fsck - The UNIX File System Check Program.

SEE ALSO
     fs(5), fstab(5), fsck(8), fsdb(8), newfs(8), reboot(8)

HISTORY
     A fsck_ext2fs utility appeared in NetBSD 1.3.

AUTHORS
     fsck_ext2fs was written by Manuel Bouyer <bouyer@NetBSD.org>.

NetBSD 8.0                    September 11, 2016                    NetBSD 8.0