Thanks for reply
Here is the output:
root@openmediavault:~# du -d1 -h -x /
12M /etc
12K /media
344K /root
160K /opt
16K /lost+found
4.0K /lib64
4.0K /sharedfolders
13M /bin
613M /var
4.0K /mnt
446M /boot
16K /srv
4.0K /export
4.0K /home
2.8G /usr
3.1G /lib
15M /sbin
6.9G /
What to do next ??