Working with inittab configuration file
The init process determines which runlevel to boot up by parsing the following statement in inittab configuration file.
id:5:initdefault:
In the above initdefault statement, the runlevel value is set to "5", which means that the init should boot the machine in GUI mode with full networking support. If tou want to boot with out GUI mode with full networking support, enter a runlevel value "3" as shown below. Please visit the following link to learn about different runlevels in linux.
id:3:initdefault:
There are four other default commands in /etc/inittab.
The first one is -
ca::ctrlaltdel:/sbin/shutdown -t3 -r now
The above command captures the CTRL-ALT-DELETE key combination and associates it with the shutdown command shown, which executes the command after 3 seconds, in reboot mode.
The second and third are -
pf::powerfail:/sbin/shutdown -f -h +2 "Power Failure; System Shutting Down"
pr:12345:powerokwait:/sbin/shutdown -c "Power Restored; Shutdown Cancelled"
The above two commands are associated with the signal from an UPS (Uninterrupted Power Supply). If you have a UPS connected to your system and a power failure occurs, the UPS should take over powering your computers. First command warns the users and shut down after 2 minutes and the second command cancels the shutdown if the power is restored within the timelimit.
The fourth command is related with graphical display which will run if the default runlevel is 5.
x:5:respawn:/etc/X11/prefdm -nodaemon
A virtual console is a command line where you can log into and control Linux. As RHEL is a multiterminal operating system, you can log into Linux, even with the same user ID, several times.
By default, RHEL is configured with six virtual consoles and the seventh one is the X display, which is the GUI desktop. You can configure up to twelve virtual consoles in /etc/inittab.
1:2345:respawn:/sbin/mingetty tty1
2:2345:respawn:/sbin/mingetty tty2
3:2345:respawn:/sbin/mingetty tty3
4:2345:respawn:/sbin/mingetty tty4
5:2345:respawn:/sbin/mingetty tty5
6:2345:respawn:/sbin/mingetty tty6