Updated: 2021/Apr/14

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

     fsck_lfs - Log-structured File System consistency check and interactive

     fsck_lfs [-dfpqU] [-b block] [-m mode] [-y | -n] filesystem ...

     fsck_lfs 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 design of LFS takes care that no filesystem inconsistencies can
     happen unless hardware or software failures intervene.  fsck_lfs will
     report and optionally correct any such inconsistencies.

     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_lfs will print the number of files on that filesystem,
     the number of used and free blocks, and the percentage of fragmentation.

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

     Without the -p option, fsck_lfs 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 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_lfs will default to a -n action.

     The following flags are interpreted by fsck_lfs:

     -b block    Use block as the super block for the filesystem.

     -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_lfs will not check the
                 file system.  This option forces fsck_lfs to check the file
                 system, regardless of the state of the clean flag.

     -m mode     Use mode specified in octal as the permission bits to use
                 when creating the lost+found directory rather than the
                 default 1700.  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_lfs
                 except for `CONTINUE?', which is assumed to be affirmative;
                 do not open the filesystem for writing.

     -p          Specify "preen" mode.  Currently, in this mode fsck_lfs does

     -q          Quiet mode, do not output any messages for clean filesystems.

     -U          Resolve user ids to user names.

     -y          Assume a yes response to all questions asked by fsck_lfs;
                 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.
           2.   Blocks claimed by an inode outside the range of the
           3.   Incorrect link counts.
           4.   Size checks:
                      Directory size not a multiple of DIRBLKSIZ.
                      Partially truncated file.
           5.   Bad inode format.
           6.   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.
           7.   Super Block checks:
                      More blocks for inodes than there are in the filesystem.
           8.   Index File checks:
                      "In use" inodes on free list, or free inodes not on free
                      Segment block counts incorrect, or "clean" segments
                      containing live data.

     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.

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

     fstab(5), fsck(8), newfs_lfs(8), reboot(8)

     The fsck_lfs program was first made available in NetBSD 1.4.

     Most of the fsck_lfs program was taken from fsck_ffs(8); what was not was
     written by Konrad Schroder <perseant@NetBSD.org>.

NetBSD 9.99                      July 12, 2014                     NetBSD 9.99