Hi guys,

I was just trying to mess with my RHEL 6.7 VM server and while formatting I noticed that two same size attached HDDs are showing different messages which is:

For sdb:
This filesystem will be automatically checked every 28 mounts or 180 days, whichever comes first. Use tune2fs -c or -i to override.

For sdc:
This filesystem will be automatically checked every 31 mounts or 180 days, whichever comes first. Use tune2fs -c or -i to override.

I wonder why there is this difference of 28 and 31 mount values ?

Any explanation ?

Thanks in advance.

More details:

[root@linuxtest ~]# mkfs.ext4 /dev/mapper/sdb1_vg-sdb1_lv
mke2fs 1.41.12 (17-May-2010)
Filesystem label=
OS type: Linux
Block size=4096 (log=2)
Fragment size=4096 (log=2)
Stride=0 blocks, Stripe width=0 blocks
65024 inodes, 260096 blocks
13004 blocks (5.00%) reserved for the super user
First data block=0
Maximum filesystem blocks=268435456
8 block groups
32768 blocks per group, 32768 fragments per group
8128 inodes per group
Superblock backups stored on blocks:
32768, 98304, 163840, 229376

Writing inode tables: done
Creating journal (4096 blocks): done
Writing superblocks and filesystem accounting information: done

This filesystem will be automatically checked every 28 mounts or 180 days, whichever comes first. Use tune2fs -c or -i to override.


[root@linuxtest ~]# mkfs.ext4 /dev/mapper/sdc_vg-sdc_lv
mke2fs 1.41.12 (17-May-2010)
Filesystem label=
OS type: Linux
Block size=4096 (log=2)
Fragment size=4096 (log=2)
Stride=0 blocks, Stripe width=0 blocks
65024 inodes, 260096 blocks
13004 blocks (5.00%) reserved for the super user
First data block=0
Maximum filesystem blocks=268435456
8 block groups
32768 blocks per group, 32768 fragments per group
8128 inodes per group
Superblock backups stored on blocks:
32768, 98304, 163840, 229376

Writing inode tables: done
Creating journal (4096 blocks): done
Writing superblocks and filesystem accounting information: done

This filesystem will be automatically checked every 31 mounts or 180 days, whichever comes first. Use tune2fs -c or -i to override.
[root@linuxtest ~]#

[root@linuxtest ~]# df -h
Filesystem Size Used Avail Use% Mounted on
/dev/mapper/sdb1_vg-sdb1_lv
985M 1.3M 932M 1% /sdb
/dev/mapper/sdc_vg-sdc_lv
985M 1.3M 932M 1% /sdc

Guess: Mkfs does this on purpose so that not all filesystems are checked at the same time. The man page for tune2fs talks about staggering max-mount-counts, which points in this direction.

If I am right though, this purpose is defeated by the 180 days horizon. Typical servers aren't rebooted every week.

That's a (very) old version of e2fsprogs. Several years go (2011) this all changed so that the limits are ignored now by default. If a check is needed at any time a ext4 (at least) f/s is mounted, it will run automagically. The old behaviour can be forced by a mke2fs.conf option. Here is a quote from the current manpage that explains the different numbers the OP queried.