How can I check my hard disk usage in Linux?

Once you are connected to the server via SSH, run the following command:
# df -h

This will output the usage of each partition in the server. To list the size of a specific directory, run the following command:
# du -sh /home/

If you want to list all the subdirectory sizes under /home, run the following command:
# du -sh /home/*

The output of the 'df' command will show you overall disk usage. To find out how much space a give directory is used us the 'du -s ' command.