important bash commands for system administration

As you know the terminal is the power tool that every linux user may have to come in contact even once in their computer life. Here is a post about controlling and managing your system using the gnome terminal.

How to shut down the system
 
$shutdown -h now

The word 'now' is enough to shutdown the system at this instant itself. You must be sudo before executing this command. You can specify the time instead of the word 'now' so that the system will shut after that time limit. Other  valid  formats  are  +m,  where m is the number of minutes to wait until shutting down and hh:mm which specifies the time on the 24hr clock.

       -r     reboots the system after shutdown

       -h    Requests  that  the system be either halted
              or powered off after it has been brought 
              down

       -c    Cancels  a  running  shutdown.   TIME is not 
              specified with this option, the first     
              argument is MESSAGE.

       -k    Only send out the warning messages and 
              disable  logins,  do  not actually bring the 
              system down.

How to take the root shell prompt
 
You can take the root shell prompt using the root password as follows

$ sudo su
 
How to switch between virtual consoles

In most debian based systems there are six switchable VT100-like character consoles available to start the command shell directly on the Linux host. Unless you are in a GUI environment, you can switch between the virtual consoles by pressing the Ctrl - Alt keys and one of the F1 --- F6 keys simultaneously. Each character console allows independent login to the account and offers the multiuser environment. You can get back to the X Window System, normally running on the virtual console 7, by pressing Ctrl - Alt - F7

Alternatively we can use the command chvt to  switch between virtual consoles from the command line
 
$ chvt  3        (switches to 3rd console )

 
How to quit the terminal

Press Ctrl + D to terminate the shell activity.



To create a new user account 


To create a new user account from the terminal type in as follows...


$ adduser carbon


This will add the user with name 'carbon'.  You can remove this user and it's home directory by using the following command.

$ deluser --remove-home carbon