Cpanel WHM Error filesystem mounted at / on this server is running out of disk space.

while I open the WHM or Cpanel I got the following error message.

The file system mounted at / on this server is running out of disk space. c Panel operations have been temporarily suspended to prevent something bad from happening. Please ask your system admin to remove any files not in use on that partition.

REASON CAUSE FOR THE PROBLEM
Root partition size is full.
root@centos [~]# df -kl /
Filesystem 1K-blocks Used Available Use% Mounted on
/dev/sda5 10153988 10087512 0 100% /
Here you can confirm the Root partition is full.
Then I decided which directory or document which will take the more space.Go to the root partition
#cd /
Run the following Command
#du -sh *
 Then here I find the backup directory which will take the more space.

SOLUTION FOR THAT PROBLEM
Then I create the new partition only for the backup directory.
Using fdisk utility
#fdisk -l >> n create the new disk
Then I mount the backup directory to the new partition which one I created recently.
Then I edit the /etc/fstab
/dev/sdb1 /backup ext3 defaults,noexec 0 0
Here I mount backup document to the specific individual partition.
Then the problem has been resolved.
Now the root partition has been taken the only less space 5%.
The filesystem mounted at / on this server is running out of disk space. c Panel operations have been temporarily suspended to prevent something bad from happening. Please ask your system admin to remove any files not in use on that partition.