During a migration from one server to another I used nfs to mount the remote older server to the new server to rsync content across faster.
After the process was completed I deleted the older server, but didn’t unmount the drive before hand.
Because of this, every time that I tried to ls on the home directory (where the mount was), or use df -h to check the disk usage it would hang.
You can use umount -f -l ~/the-folder-mounted, and that will fix the problem.
-f– Force unmount (in case of an unreachable NFS system). (Requires kernel 2.1.116 or later.)-l– Lazy unmount. Detach the filesystem from the filesystem hierarchy now, and cleanup all references to the filesystem as soon as it is not busy anymore. (Requires kernel 2.4.11 or later.)