Speaking for a debian based system, here is a short list of very essential and useful commands:
- To update your system: agt-get update, then apt-get upgrade. Also see: Installing/updating software on any Linux system.
- The whole domain of /etc/init.d/xxx scripts, most prominently /etc/init.d/apache2 force-reload.Also compare these posts:
How do I exit the X Server from command line?
How do I restart services on Linux?
- Directory listings in awell formatted way: ls -al, or for another dir than the current: ls /path/to/dir -al
- To follow changes in a file, like a logfile: tail -f /var/log/apache2/error.log
- To edit files, without the need to learn vi use nano: nano /path/to/file.txt