Tuesday, 11 October 2011

Changing Runlevels at Boot Time -- Oracle Linux / Red Hat Linux

Changing Runlevels at Boot Time
Under Red Hat Linux, it is possible to change the default runlevel at boot time.

If using LILO, access the boot: prompt by typing [Ctrl]-[X]. Then type:

linux <runlevel-number>

In this command, replace <runlevel-number> with either the number of the runlevel to boot into (1 through 5), or the words single or emergency.

If using GRUB, follow these steps:

In the graphical GRUB boot loader screen, select the Red Hat Linux boot label and press [e] to edit it.

Arrow down to the kernel line and press [e] to edit it.

At the prompt, type the number of the runlevel you wish to boot into (1 through 5), or the words single or emergency and press [Enter].

You will be returned to the GRUB screen with the kernel information. Press the [b] key to boot the system

BOOTING IN RUNLEVEL 3 ( With Grub ) == OEL Linux

There are occasions you want to boot in non-graphical mode ( in runlevel 3 ) for troubleshooting because the system fails to boot the usual way, X fails to start or some module it fails to load.

Here is how you do it when Grub is your boot loader:

At the grub boot menu press the E key. Next select the distro you want to boot and press the E key again. Now select the line with "kernel /boot/vmlinuz" and hit the E key one more time. Now type a space and the number 3 at the end of that line, so for example from:

kernel /boot/vmlinuz-2.6.17 ro root=/dev/hda6


kernel /boot/vmlinuz-2.6.17 ro root=/dev/hda6 3

Finally press the B key and your distro will boot in runlevel 3

NOTE: Runlevel 3 does not work in Ubuntu . . . . use the "rescue mode" you see in the Ubuntu boot menu.

NOTE 2: In recent Mandriva versions Grub has a graphical menu where you can press F2 to edit boot options . . . simply add the number 3 and press the Enter key to boot in runlevel 3.

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