Information between the disk information in the Dashboard and disk information in the Disk usage are different.
Expected feature: The same information to be displayed
Occured feature: The root partition has one size in the Dashboard and another size in the disk usage…
IIRC, duc uses the so called apparent size, i.e. the sum of the size of all files, while the dashboard uses the du (disk usage) command which reports used space. Think of sparse files, you can have a file of ten of G of size which uses only some bytes on disk.
The problem is not df, that one is correct. The issue is the myriad of symlinks that get counted multiple times when showing the graphic version. This is because the way Nethserver works, /home is the same as /var/lib/nethserver/home and the same fun happens again when you use FTP with system users, as this will utilise home aka /var/lib/nethserver/home again.
The df command is always right, the graphic might be wrong due to following symlinks or bindmounts while aggregating the files in those folders. If you could make it so that it ignores symlinks or bind mounts, this issue should resolve itself.
Sorry if I necromanced this topic, I called it in as question, and got referred here.