To check hard disk usage on Ubuntu from a terminal (command line), issue the following command in your terminal.
liping:~$ df -h
-h stands for human which makes it readable by us humans, otherwise the file size will be in bytes:)
After you issue the command, you would see your disk usage similar to the info given below.
Filesystem Size Used Avail Use% Mounted on /dev/sda7 68G 23G 43G 35% / udev 10M 0 10M 0% /dev tmpfs 800M 1.6M 798M 1% /run tmpfs 5.0M 0 5.0M 0% /run/lock /dev/sda6 264G 173G 78G 69% /home tmpfs 3.2G 992K 3.2G 1% /tmp . . .