E2MMPSTATUS(8)            (August 2021)            E2MMPSTATUS(8)

     NAME
          e2mmpstatus - Check MMP status of an ext4 file system

     SYNOPSIS
          e2mmpstatus [-i] <filesystem>

     OPTIONS
          -i   prints out the MMP information rather than check it.

     DESCRIPTION
          e2mmpstatus is used to check Multiple-Mount Protection (MMP)
          status of an ext4 file system with the mmp feature enabled.
          The specified file system can be a device name (e.g.
          /dev/hdc1, /dev/sdb2), or an ext4 file system label or UUID,
          for example UUID=8868abf6-88c5-4a83-98b8-bfc24057f7bd or
          LABEL=root.  By default, the e2mmpstatus program checks
          whether it is safe to mount the file system without taking
          the risk of mounting it more than once.

          MMP (multiple-mount protection) is a feature that adds pro-
          tection against the file system being modified simultane-
          ously by more than one node.  It is NOT safe to mount a file
          system when one of the following conditions is true:
               1. e2fsck is running on the file system.
               2. the file system is in use by another node.
               3. The MMP block is corrupted or cannot be read for
          some reason.
          The e2mmpstatus program might wait for some time to see
          whether the MMP block is being updated by any node during
          this period.  The time taken depends on how frequently the
          MMP block is being written by the other node.

     EXIT CODE
          The exit code returned by e2mmpstatus is 0 when it is safe
          to mount the file system, 1 when the MMP block shows the
          file system is in use on another node and it is NOT safe to
          mount the file system, and 2 if some other failure occurred
          that prevents the check from properly detecting the current
          MMP status.

     SEE ALSO
          dumpe2fs(8), e2fsck(8), fstab(5), fsck(8),

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