How to change run level in Linux (i.e. Red Hat / CentOS)?

• Runlevel0 is halt
• Runlevel1 is single-user
• Runlevels2-5 are multi-user
• Runlevel6 is for rebooting system

For example, typing the init3 command will move system to run level3:

from CLI type :

#init LEVELNO

its very simple. 

login as root  and then execute the command

vi /etc/inittab

There you will find a line just like this. 

id:5:initdefault:

change the value1-5 depends on your need. Just as an example, the above line depicts that it will use run level5 which is primiarily used for GUI, you can change value to3 for multi user CLI. which is preferred for system admin tasks. 

# Default runlevel. The runlevels used are:

#  0 - halt (Do NOT set initdefault to this)

#  1 - Single user mode

#  2 - Multiuser, without NFS (The same as3, if you do not have networking)

#  3 - Full multiuser mode

#  4 - unused

#  5 - X11

#  6 - reboot (Do NOT set initdefault to this)

 once you have changed the value, then save this file and exit.. dont forget to reboot your linux box. 

In Linux,6 run levels are available.  It is start from0 to6

For identifying current run level, enter following command

# who -r 

or 

#runlevel

For changing to any other runlevel, enter following command

#init <runlevel number>

For small description about6 runlevels

#  0 - halt (Do NOT set initdefault to this)

#  1 - Single user mode

#  2 - Multiuser, without NFS (The same as3, if you do not have networking)

#  3 - Full multiuser mode

#  4 - unused

#  5 - X11

#  6 - reboot (Do NOT set initdefault to this)

just with root privilage write "init" before the level you want