Major administration tasks include user account management, hardware and software management, system backup, system monitoring performance tuning, troubleshooting system problems, security auditing, and documentation.
System administration in Linux (or Unix) is usually done using shell instead of using fancy GUI tools, even though there are GUI tools for some administration tasks. Using shell, we can go beyond the limitation imposed by the complicated GUI tools. Avoiding point-n-click, it is a lot faster to use shell. Moreover, using shell, system administration tasks can easily be automated and be done in a lot more creative, yet economical manner.