What are Linux run levels and how can I see which programs and applications are running in each run level?
A. Linux has 6 different run levels (or operating modes): rc1.d – Single User Mode rc2.d – Single User Mode with Networking rc3.d – Multi-User Mode – boot up in text mode rc4.d – Not yet Defined rc5.d – Multi-User Mode – boot up in X Windows rc6.d – Shutdown Each mode has it’s own list of settings for what services to start and what services to shutdown. Not only does this list contain what is supposed to be running, but also what order each service should be started in. The ‘chkconfig’ command will list all the registered services and display their status at each different run level. Most of the time when your server boots up it will start in run level 3 or 5 depending on what it is set to. This setting can be found in the file /etc/inittab. If you ever want to change what mode your server defaults to on bootup, just edit that file, but NEVER change it to run level 6 or else you will set your server to shutdown on bootup. Example: [root@ernest root]# chkconfig –list (will list the fol
