Ubuntu Disk Stuff – running fsck at next reboot

Written by James McDonald

September 10, 2008

How to schedule a disk check for the next reboot. As root or using sudo do the following:

Method 1: Use the forecfsck file method

touch /forcefsck
shutdown -r now

Note: This command seems to check all partitions when run

Method 2: Up the mount count above the fsck check limit

Use this to identify what mounted partition you want to check

df -h
Filesystem            Size Used Avail Use% Mounted on
/dev/sda2              88G   81G  2.5G  98% /

On a LVM system the path to the device can be quite long

df -h
Filesystem            Size  Used Avail Use% Mounted on
                       36G  913M   34G   3% /

/dev/sda5             236M   19M  206M   9% /boot

Check the current “Maximum mount count” and “Mount Count” values

tune2fs -l /dev/sda2 | grep -E '(Max|Mount)'
Mount count:              11
Maximum mount count:      36

Then set the actual “Mount count” to something higher

tune2fs -C 100 /dev/sda2

Check it out

tune2fs -l /dev/sda2 | grep Mount
Mount count:              100

Then reboot and wait for the disk check to finish, remember the bigger the volume the longer it takes. Make a cup of $BEVERAGE.

Ever wondered how to identify what partition is mentioned in /etc/fstab with

UUID=a0584727-1c8b-48df-867b-9e3b5a453ff7 /               ext3    defaults,errors=remount-ro 0       1

Use tune2fs and you will find the answer

tune2fs -l /dev/sda2 | grep UUID
Filesystem UUID:          a0584727-1c8b-48df-867b-9e3b5a453ff7

Now how would you apply a new UUID to a partition
tune2fs -U `uuidgen` /dev/sda3

tune2fs -l /dev/sda3 | grep UU
Filesystem UUID: 293512d5-fbb9-4a0a-9d50-ce347a3e0091

So it’s easy then to reference that in /etc/fstab

UUID=293512d5-fbb9-4a0a-9d50-ce347a3e0091            /media/sda3  ...

What is a UUID? It’s a Universally Unique Identifier. Theoretically, the way it’s generated means that you wont get a duplicate anywhere. You see them used a lot where uniqueness is needed (check the Windows Registry).

It is a better system then using labels to identify partitions because a label can be easily duplicated.

If you are old school Redhat then you can use e2label and apply a label to the partition:

e2label /dev/sda3 MYDISK

Then in /etc/fstab you can refer to the volume thusly

LABEL=MYDISK     /media/sda3     ext3    defaults        0       2

Note: I had to reboot for the above LABEL= change to take affect. The MYDISK label needs to appear in /dev/disk/by-label/MYDISK for a mount operation to work.

It’s probably better to make the label to be the same as the mount point. For example

e2label /dev/sdb12 /u2

Then add that to /etc/fstab

LABEL=/u2              /u2           ext3       defaults ....

would be mounted at /u2 so you know exactly where the partiton is going.


  1. Vasilis

    I tried to set the mount count in a number bigger than the maximum count number in order for the disks to be checked on the next reboot, but it doesn’t seem to work. The mount count number is raised and set to the right value and is incremented every time I reboot but checking on my disk isn’t forced.
    Do u have any clue on what is wrong?

  2. James

    I had some confusion between “Mount count” and “Maximum mount count” it’s “Mount Count” you need to set but I don’t think that’s your issue.

    sudo tune2fs /dev/sda3 -l | grep -i mount
    Last mounted on:
    Default mount options: (none)
    Last mount time: Sat Sep 13 07:20:24 2008
    Mount count: 3
    Maximum mount count: 39

    Have a look in /etc/fstab you should see something like:
    UUID=48c9bea8-3b6f-4636-a83a-22c803ed1f03 /boot ext3 relatime 0 2

    The last value, in this case a 2, is the order in which the partition is checked on a disk / is usually 1 and the other file partitions go up from there. If it’s set to zero then the filesystem won’t be checked. I think people set this to 0 to stop being interrupted by a disk check.

    Also check man fstab for information

  3. neverman

    Method 1 was the silver bullet for my unbootable sick ubuntu machine!
    Thanks for the tip!



  1. Should I run fsck on boot for an amazon ec2 image? | MoVn - Linux Ubuntu Center - [...] read this blog post which mentions that if the /etc/fstab <pass> column is set to 0 then a disk…
  2. Run fsck on reboot | Useful snippets - [...] Source [...]

Submit a Comment

Your email address will not be published. Required fields are marked *

This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.

The reCAPTCHA verification period has expired. Please reload the page.

You May Also Like…