/etc/inittab
The /etc/inittab file holds instructions for your system on how to manage terminal devices. A line in the /etc/inittab file has four basic components: an ID, a runlevel, an action, and a process.Terminal devices are identified by ID numbers, beginning with 1 for the first device. The runlevel at which the terminal operates is usually 1. The action is usually respawn, which means to run the process continually. The process is a call to the mingetty, mgetty, or agetty with the terminal device name.
Wrong editing in this file could be dangerous even it could crash Linux system. We suggest you to take back up first before editing in this file.
#cp /etc/inittab /root
After taking backup open /etc/inittab file
[root@ns1 ~]# vi /etc/inittab
Change Default Run Level
Linux have seven run levels. Functions of all run level are
# Default runlevel. The runlevels
used by RHS are:
# 0 - halt (Do NOT set initdefault to this)
# 1 - Single user mode
# 2 - Multiuser, without NFS (The same as 3,
if you do not have networking)
# 3 - Full multiuser mode
# 4 - unused
# 5 - X11
# 6 - reboot (Do NOT set initdefault to this)
During
system startup process Linux check this file to determines which
runlevel it should be boot by looking at the initdefault directive in
/etc/inittab. For example, the entry
# Default runlevel. The runlevels
used by RHS are:
# 0 - halt (Do NOT set initdefault to this)
# 1 - Single user mode
# 2 - Multiuser, without NFS (The same as 3,
if you do not have networking)
# 3 - Full multiuser mode
# 4 - unused
# 5 - X11
# 6 - reboot (Do NOT set initdefault to this)
id:5:initdefault:
To change this default runlevel locate this tag id:5:initdefault: Now replace the value 5 to 3 as show here to boot system in run level 3 Save the file and restart the system it will boot now in run level 3.
# 6 - reboot (Do NOT set initdefault to this)
#
id:3:initdefault:
# System initialization.
si::sysinit:/etc/rc.d/rc.sysinit
How to disable ALT+CTRL+DEL key combination
By default ALT+CTRL+DEL key combination is used to restart the system. This default behavior is also controlled by this tag in /etc/inittab file.
# Trap CTRL-ALT-DELETE
#ca::ctrlaltdel:/sbin/shutdown
-t3 -r now
# Trap CTRL-ALT-DELETE
#ca::ctrlaltdel:/sbin/shutdown
-t3 -r now
By some mean if you don't want to use ATL+CTRL+DEL key to restart the system. Put a hash # sign to this tag and save the file and restart the system. Now you cannot restart the by ATL+CTRL+DEL key.
How to increase the number of virtual consoles
Virtual consoles are configured in /etc/inittab. By default, RHEL is configured with six virtual consoles. You can configure up to twelve virtual consoles in /etc/inittab.
Here are the default /etc/inittab entries for the first six virtual consoles:
# Run gettys in standard
runlevels
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
To increase the number of virtual console copy the configuration line of last virtual console and past just below the default line and change the number as shown in image. Save file and restart the system.
# Run gettys in standard
runlevels
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
7:2345:respawn:/sbin/mingetty
tty7
8:2345:respawn:/sbin/mingetty
tty8
9:2345:respawn:/sbin/mingetty
tty9
After restart you can login in to increased terminals by pressing ALT+Funcation key combinations.
[root@ns1 ~]# tty
/dev/tty7
[root@ns1 ~]#
Other use full commands
#init [run level]
With this command you can switch between run levels. For example to go on run level one type
#init 1
#telinit 1
Same as init. This will also take you on run level one.
#runlevel
To know on which run level are you working now use runlevel commands.
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