A useful example of un-mounting and mounting manually would be if a software update is to be performed, and users are not allowed to access the system. In this case, the system administrator could send an alert for the users to log-off the system due to system maintenance, un-mount the '''/home''' directory to prevent any regular users to login, and then update the software. Once the software has been updated, then mount the '''/home''' directory to allow user access. [[Image:disk_usage.png|thumb|400px|right|The '''df''' and '''du''' commands are useful tools for Linux system administrators to flag disk space issues and investigate their causes.]]Since administrators may need to log into the system with their regular user accounts, and then issue the '''su''' command to connect into the '''root''' account, there is a dilemma: How can /home be unmounted when you are logged in as a regular user. The solution would be to reboot the machine and boot into single-user mode (demonstrated in '''lab3'''). This allows the system administrator to connect into the system in a text-based system automatically logged in as root. Remember that '''the root account has its own home directory''' (i.e.'''/root''') which is not associated with the ''/home'' directory (which can now be un-mounted and mounted for system maintenance).