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Runlevel

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A runlevel (or "run level") is a mode of operation that can specify what resources are available.

According to The Gentoo Handbook Part 2, Chapter 4, Initscripts

"You have seen that init uses a numbering scheme to decide what runlevel it should activate. A runlevel is a state in which your system is running and contains a collection of scripts (runlevel scripts or initscripts) that must be executed when you enter or leave a runlevel.

In Gentoo, there are seven runlevels defined: three internal runlevels, and four user-defined runlevels. The internal runlevels are called sysinit, shutdown and reboot and do exactly what their names imply: initialize the system, powering off the system and rebooting the system.

The user-defined runlevels are those with an accompanying /etc/runlevels subdirectory: boot, default, nonetwork and single. The boot runlevel starts all system-necessary services which all other runlevels use. The remaining three runlevels differ in what services they start: default is used for day-to-day operations, nonetwork is used in case no network connectivity is required, and single is used when you need to fix the system."

Standard Gentoo Run Levels

Standard Run Level Definitions

l0:0:wait:/sbin/rc shutdown
l1:S1:wait:/sbin/rc single
l2:2:wait:/sbin/rc nonetwork
l3:3:wait:/sbin/rc default
l4:4:wait:/sbin/rc default
l5:5:wait:/sbin/rc default
l6:6:wait:/sbin/rc reboot


Run Level Explanation
0 - Halts the computer
1 - Log in as single user root (doesn't ask for password, useful for if you've forgotten or accidentally altered the root password and need to change it without a Gentoo install CD)
2- Multi-user without network access
3,4,5 - Full multi-user with network access (typical operation, all three run levels should work in the same manner since they all reference default)
6 - Reboot (can execute this by calling reboot on the command line)


Custom Gentoo Run Levels


Custom run levels beyond what is offered as defaults can be created as noted in HOWTO_create_a_run_level
All custom run levels have an associated directory in gentoo:/etc/runlevels

GRUB and LILO


GRUB and LILO allows one to boot up a non-default mode of operation by adding the softlevel parameter after specifying the kernel location or by including the number of the run level as a kernel option.

Note: “softlevel=single” may not have the same effect as adding a “1” as a kernel option

Goto TIP_Booting_into_single_user_mode for examples.


Last modified: Fri, 05 Sep 2008 08:47:00 +0000 Hits: 3,102