Linux administration activities are similar to any Unix system.
The important components are hardware device administration, files system, users administration, programs packs administration, services administration, system security ensuring and automation tasks.
Most of system administrator interactions with Linux operating system will be done through the command line interface (shell) and text configuration files.
The components of a GNU / Linux / Distributions
An GNU/Linux operating system consists of core (kernel), Linux and applications running over it.
One of the most significant application is the command interpreter (the shell). On most of Linux distributions the shell is Bash.
The shell acts as an intermediary between user and core. The shell transforms users command in to process which is using the core to complete a task.