How do I check how many times the root-file system can be mounted before it is auto checked?

Question

How do I check how many times the root file system can be mounted before it is auto checked? I'm wondering as I want to see on my system how many times it can be mounted.

Answer 1

If your root file system is ext4, you can use tune2fs to check (and also to modify) how many times it can be mounted before it is autochecked. See man tune2fs,

 -l     List the contents of the filesystem superblock, including the
        current values of the parameters that can be set via this program.

Using my root file system as an example:

sudo tune2fs -l /dev/sda1

or more focused

$ LANG=C sudo tune2fs -l /dev/sda1|grep -A4 'Mount count:'
[sudo] password for sudodus: 
Mount count:              30
Maximum mount count:      40
Last checked:             Tue Dec 25 05:50:43 2018
Check interval:           2592000 (1 month)
Next check after:         Thu Jan 24 05:50:43 2019

You can have both a number of mount criterion and a time criterion, and (during boot) when the first criterion is satisfied, there will be a check.

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Please notice that in many new versions (of tune2fs and of linux file systems), mount-count-dependent checking is disabled by default to avoid unanticipated long reboots while e2fsck does its work.

   -c max-mount-counts
          Adjust the number of mounts after which the filesystem will be checked by
          e2fsck(8).  If max-mount-counts is 0 or  -1,  the  number  of  times  the
          filesystem is mounted will be disregarded by e2fsck(8) and the kernel.

          Staggering  the  mount-counts  at  which filesystems are forcibly checked
          will avoid all filesystems being checked at one time when using journaled
          filesystems.

          Mount-count-dependent  checking is disabled by default to avoid unantici‐
          pated long reboots while e2fsck does its work.  However, you may wish  to
          consider  the  consequences  of  disabling mount-count-dependent checking
          entirely.  Bad disk drives, cables, memory, and  kernel  bugs  could  all
          corrupt  a  filesystem  without marking the filesystem dirty or in error.
          If you are using journaling on  your  filesystem,  your  filesystem  will
          never  be marked dirty, so it will not normally be checked.  A filesystem
          error detected by the kernel will still force an fsck on the next reboot,
          but it may already be too late to prevent data loss at that point.

          See also the -i option for time-dependent checking.