Running levels in Linux

標籤：linux   running level   

Linux system has several running levels:

0 - shutdown

1 - single user

2 - multi user without Internet services

3 - multi user with Internet services

4 - unused and reservered

5 - GUI

6 - Reboot

We can use the "Init *" command to change running level of the system.

To change the default setting of running level, we need to edit the file "/etc/inittab":

"id:*:initdefault".

Often, we may have probles of setting a wrong default running level. We need to press "e" on the interface of grub guidence. Then we need to add 1 to the second line. The reason is that Linux will read inittab file before boot except for running level 1. We can go to running level 1 and then change the "/etc/inittab" file.

Basically, this is a bug for the Linux system and it is necessary for system admin to set passwords for grub interface.

In running level 1 - single user mode, we can directly change the password of root.