What explains the discrepancy in usage (
82 GB vs
13 GB) that I see below?
$ df -h / Filesystem Size Used Avail Use% Mounted on /dev/sda2 96G 82G 9.9G 90% /
$ sudo du -cshx / 13G / 13G total
-x option is a false friend as its purpose is to skip things. That option never gives you the complete picture.
To get a complete listing, use bind mounts and then
baobab or whatever you wish on the bound directory without skip options:
mkdir /mnt/root mount --bind / /mnt/root ncdu /mnt/root
Then you might discover you have lots of stuff in
/mnt/backup (because it wasn't mounted when the backup task ran), or a giant file in
/dev (result of a
dd if=/dev/zero of=/dev/sdx when no
/dev/sdx existed and no tmpfs was mounted in
It could also be a deleted file still used by a process, but people don't usually ask about it as it's gone after reboot. It could also be a filesystem inconsistency, but that too would be gone after reboot (if it forces
fsck in the process).