File System inconsistency Post: 65464

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Top Forums UNIX for Dummies Questions & Answers File System inconsistency Post 65464 by Perderabo on Saturday 5th of March 2005 09:12:55 AM

03-05-2005

Administrator Emeritus

I'm not following all of this, but here are a few comments. Are you sure that /usr is mounted? Are you sure that you don't know the device name? It's not easy to find out that a file system is mounted without also obtaining the device name. For example, with the "df" command, the device name is the first field. You can just examine /etc/fstab to get the device name. But you should not actually need the device name. Modern versions of fsck will look it up in /etc/fstab. So simply:
fsck /usr
really should work.

Ideally you should find some way to umount /usr or arrange that it was never mounted prior to fsck. A boot cd (can linux really boot from a diskette?) would be a good option. You're right that running fsck on a mounted filesystem is very dangerous. This is because some of the data from that filesystem is sitting in buffer cache. When this cache is written out, it will intermix with the data written by fsck and scramble the filesystem. So you need to do the following sequence of commands:
sync
<wait 10 seconds or so>
fsck /usr
reboot -n

The first sync will flush out any changed data in / or any other mounted filesystems. You need to wait until the disk writes complete. Then run fsck.
Then immediately reboot without syncing. Also during this entire procedure, almost nothing else must be happening. It is relatively safe in single user mode. This is not completely safe, but your system is not usuable anyway, so it is what I would try. There is a risk of damaging other mounted filesystems. The first sync together with minimizing activity should mitigate this danger. If you decide to try it, please post back and let us know how it works.

However, even if this does work, you may not be home free. fsck may not be able to repair your disk. "attempt to read blocks from filesystem resulted in short read" make me think that your disk may be bad in a hardware sense. fsck cannot repair broken hardware.

Whether or not fsck seems to work, you must immediately do the "reboot -n". Good luck.

Perderabo

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LEARN ABOUT REDHAT

fsck.minix

FSCK.MINIX(8)                                                  System Administration                                                 FSCK.MINIX(8)

NAME

       fsck.minix - check consistency of Minix filesystem

SYNOPSIS

       fsck.minix [options] device

DESCRIPTION

       fsck.minix performs a consistency check for the Linux MINIX filesystem.

       The  program assumes the filesystem is quiescent.  fsck.minix should not be used on a mounted device unless you can be sure nobody is writ-
       ing to it.  Remember that the kernel can write to device when it searches for files.

       The device name will usually have the following form:

              /dev/hda[1-63]   IDE disk 1
              /dev/hdb[1-63]   IDE disk 2
              /dev/sda[1-15]   SCSI disk 1
              /dev/sdb[1-15]   SCSI disk 2

       If the filesystem was changed, i.e., repaired, then fsck.minix will print "FILE SYSTEM HAS CHANGED" and will  sync(2)  three  times  before
       exiting.  There is no need to reboot after check.

WARNING

       fsck.minix  should not be used on a mounted filesystem.  Using fsck.minix on a mounted filesystem is very dangerous, due to the possibility
       that deleted files are still in use, and can seriously damage a perfectly good filesystem!  If you absolutely have to run fsck.minix  on  a
       mounted  filesystem,  such  as  the  root filesystem, make sure nothing is writing to the disk, and that no files are "zombies" waiting for
       deletion.

OPTIONS

       -l, --list
              List all filenames.

       -r, --repair
              Perform interactive repairs.

       -a, --auto
              Perform automatic repairs.  This option implies --repair and serves to answer all of the questions asked  with  the  default.   Note
              that this can be extremely dangerous in the case of extensive filesystem damage.

       -v, --verbose
              Be verbose.

       -s, --super
              Output super-block information.

       -m, --uncleared
              Activate MINIX-like "mode not cleared" warnings.

       -f, --force
              Force  a  filesystem  check  even  if  the  filesystem  was  marked  as valid.  Marking is done by the kernel when the filesystem is
              unmounted.

       -V, --version
              Display version information and exit.

       -h, --help
              Display help text and exit.

DIAGNOSTICS

       There are numerous diagnostic messages.  The ones mentioned here are the most commonly seen in normal usage.

       If the device does not exist, fsck.minix will print "unable to read super block".  If the device exists, but is  not  a  MINIX  filesystem,
       fsck.minix will print "bad magic number in super-block".

EXIT CODES

       The exit code returned by fsck.minix is the sum of the following:

              0      No errors
              3      Filesystem errors corrected, system should be rebooted if filesystem was mounted
              4      Filesystem errors left uncorrected
              7      Combination of exit codes 3 and 4
              8      Operational error
              16     Usage or syntax error

AUTHORS

       Linus Torvalds <torvalds@cs.helsinki.fi>
       Error code values by Rik Faith <faith@cs.unc.edu>
       Added support for filesystem valid flag: Dr. Wettstein <greg%wind.uucp@plains.nodak.edu>.
       Check to prevent fsck of mounted filesystem added by Daniel Quinlan <quinlan@yggdrasil.com>.
       Minix v2 fs support by Andreas Schwab <schwab@issan.informatik.uni-dortmund.de>, updated by Nicolai Langfeldt <janl@math.uio.no>.
       Portability patch by Russell King <rmk@ecs.soton.ac.uk>.

SEE ALSO

       fsck(8), fsck.ext2(8), mkfs(8), mkfs.ext2(8), mkfs.minix(8), reboot(8)

AVAILABILITY

       The fsck.minix command is part of the util-linux package and is available from Linux Kernel Archive <https://www.kernel.org/pub/linux/utils
       /util-linux/>.

util-linux                                                           June 2015                                                       FSCK.MINIX(8)

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