Why does fsck show corruption when running 'fsck -n' on a mounted device when the devices are clean?

Solution Verified - Updated -

Issue

  • Issuing an fsck -n on a mounted in use device reports filesystem corruption, but when running a fsck when the device is unmounted it reports the device as clean.
  • The following types of errors are encountered when running a fsck on a mounted filesystem:
# fsck -n /dev/mapper/VolGroup-lv_test
 fsck from util-linux-ng 2.17.2
 e2fsck 1.41.12 (17-May-2010)
 Warning!  /dev/mapper/VolGroup-lv_test is mounted.
 Warning: skipping journal recovery because doing a read-only filesystem check.
 /dev/mapper/VolGroup-lv_test contains a file system with errors, check forced.
 Pass 1: Checking inodes, blocks, and sizes
 Pass 2: Checking directory structure
 Pass 3: Checking directory connectivity
 Pass 4: Checking reference counts
 Pass 5: Checking group summary information
 Block bitmap differences:  -2974075
 Fix? no

 Free blocks count wrong for group #90 (2630, counted=2629).
 Fix? no

 Free blocks count wrong (7702583, counted=7714667).
 Fix? no

 Free inodes count wrong (7285539, counted=7285465).
 Fix? no

 /dev/mapper/VolGroup-lv_test: ********** WARNING: Filesystem still has errors **********
 /dev/mapper/VolGroup-lv_test: 103645/7389184 files (0.4% non-contiguous), 21826505/29529088 blocks
  • However, when the device is unmounted an fsck reports no problems:
# fsck -fy /dev/mapper/VolGroup-lv_test

fsck from util-linux-ng 2.17.2
 e2fsck 1.41.12 (17-May-2010)
 Pass 1: Checking inodes, blocks, and sizes
 Pass 2: Checking directory structure
 Pass 3: Checking directory connectivity
 Pass 4: Checking reference counts
 Pass 5: Checking group summary information
 /dev/mapper/VolGroup-lv_test: 103645/7389184 files (0.4% non-contiguous), 21826505/29529088 blocks

Environment

  • Red Hat Enterprise Linux (RHEL)

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