Ubuntu – The “Filesystem root” has only XXX disk space remaining

disk-usagefilesystemgpartedpartitioning

The title is pretty obvious and common: the error below happens very often.
Error message

What I am asking is why does it happen. I mean, look at the output of GParted (the first 4 partition are required by Windows)
GParted output

It seems very obvious that I have a lot of free space on all the partitions. So, why the system says that the remaining space is so low?

Best Answer

  • The space that is showing as "unused" is not necessarily available to the user.

    Specifically, filesystems from the ext family reserve a number of disk blocks for system tasks as described here:

    The default amount of reserved space for these filesystems is 5%.

    From your screenshots we can see that your root filesystem is located on a partition of size 48.83GiB, so we would expect 48.83 x .05 = 2.44GiB reserved. The unused space is shown as 3.13GiB so that the available space should then be 3.13 - 2.44 = 0.69GiB - close to the 722.6MB shown by the warning message. (There will be rounding errors since the usage is only given to 2 decimals; also one is GiB and one is MB).

    You can confirm the reserved block fraction using the dumpe2fs utility. For example, using my own boot partition:

    sudo dumpe2fs /dev/sda1 | less
    

    I can see that

    Block count:              248832
    Reserved block count:     12441
    

    from which the reserved percentage is 12441/248832 x 100 = 5.00% as expected.

    The reserved block fraction can be modified using the tune2fs utility, however I would not recommend doing that in this case - it's more appropriate for large (>TB) and/or non-system disks.