About inittab and Runlevel in redhat linux server

Hello guys today we will discuss about inittab file.  inittab file is very important  .if we will do something change in inittab so we can apply very might and powerful operation. Because this file is a parent of all Linux processes. Inittab in have  0 to 6 id and Linux all control. We can also make according to our need customize terminal.

You just put #vim /etc/inittab  then you will look inittab file

if you want change something  so go to insert mod press just( i ) you go insert mod

here we will know what is 0 to 6 id and how can we use in this and what will happen when we use each id

RunLevel 0- if we will set run level 0 then our system automatically shut down again by again                                 when we start.So we will remember  0 – halt (Do NOT set initdefault to this)

RunLevel 1- RunLevel 1 is a single user mod its a very important mod in linux. when we forget                          our root password we can maintain and broken  through single user mod

RunLevel 2- Multiuser, without NFS (The same as 3, if you do not have networking) .This level in                         no used network system and NFS

RunLevel 3-  Full multiuser mode but graphical is not supported  only commands line based                                server operating system

RunLevel 4- User-definable/ this mode is use in research and  experiment 

RunLevel 5- X11 this is graphical mod if you use X11 then your server operating system                                        will use commands with graphical   

RunLevel 6- if you use run level 6 then your system will be reboot again by again when you                             start so do not set 6

you can also make customize terminal 

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

here you look inittab in like this description if u just add 8:2345:respawn:/sbin/mingetty tty8   and now reboot your system .then you will found new terminals  just press Alt+Ctrl+F8

(note – if you do something apply in inittab file so you press Esc & :wq then you file change is saved now reboot your system  .My personal advice for you if you take inittab file backup so very better for your server. Because you never loss your operating system setting  you can take the backup like this #cp /etc/inittab /etc/inittab.bak after any mistake you can take your backup file #cp /etc/inittab.bak /etc/inittab then you going your old server setting  )

Thank you

by Vishnu Sharman