Initscripts

Warning: Arch only supports systemd. Arch's old initscripts package as described on this page is obsolete and is no longer supported. All Arch users need to move to systemd.

This article is intended to give a chronological overview of the initscripts process and the system files and processes involved, providing links to relevant wiki articles where necessary. Initscripts follows the BSD init convention as opposed to the more common SysV. What this means is that there is little distinction between runlevels, since the system by default is configured to use the same modules and run the same processes on all runlevels. The advantage is that users have a simple way to configure the startup process (see rc.conf); the disadvantage is that some fine-grained configuration options that SysV offers are lost. See Adding Runlevels for a way to hack some SysV-like capabilities into Arch. See Wikipedia:init for more on the distinctions between SysV and BSD style.

init and boot scripts

The main startup process is initiated by the program init, which spawns all other processes. The purpose of init is to bring the system into a usable state, using the boot scripts to do so. As previously mentioned, initscripts uses BSD-style boot scripts. init reads the file /etc/inittab; the default inittab begins with the following:

/etc/inittab

...

# Boot to console
id:3:initdefault:
# Boot to X11
#id:5:initdefault:

rc::sysinit:/etc/rc.sysinit
rs:S1:wait:/etc/rc.single
rm:2345:wait:/etc/rc.multi
rh:06:wait:/etc/rc.shutdown
su:S:wait:/sbin/sulogin

...

The first uncommented line defines the default system runlevel (3). When the kernel calls init:

• First, the main initialization script is run, /etc/rc.sysinit (a Bash script).
• If started in single user mode (runlevel 1 or S), the script /etc/rc.single is run.
• If in any other runlevel (2-5), /etc/rc.multi is run instead.
• The last script to run is /etc/rc.local (via /etc/rc.multi), which is empty by default.

Note: You may want to read more about SysVinit.

/etc/rc.sysinit

/etc/rc.sysinit is a large startup script that configures hardware, and performs general initialization tasks. It can be identified by one of its first tasks, printing the lines:

Arch Linux
https://www.archlinux.org

The tasks of rc.sysinit are:

1. sources the /etc/rc.conf and /etc/rc.d/functions scripts.
2. displays a welcome message.
3. mounts various virtual file systems.
4. make sure rootfs is mounted read-only (if needed).
5. starts bootlogd.
6. print deprecation warnings.
7. configures the hardware clock.
8. starts udev, loads modules from the MODULES array defined in rc.conf, and waits for udev to finish processing coldplug events.
9. starts the loopback interface.
10. configures RAID, btrfs and encrypted filesystem mappings.
11. check partitions (fsck).
12. remount the rootfs in order to apply the options from /etc/fstab.
13. mounts local filesystems (networked drives are not mounted before a network profile is up).
14. start monitoring lvm groups.
15. activates swap areas.
16. configure timezone.
17. initialize the random seed.
18. removes various leftover/temporary files, such as /tmp/*.
19. sets the hostname, locale and system clock as defined in rc.conf.
20. configures the locale, console, and keyboard mappings.
21. sets the console font.
22. writes output from dmesg to /var/log/dmesg.log.

/etc/rc.sysinit is a script and not a place for settings. It sources (i.e. reads and inherits variables and functions) rc.conf for settings and /etc/rc.d/functions for the functions that produce its graphical output (nice colors, alignments, switching 'busy' to 'done', etc.). This file should not be edited as it is overwritten on upgrade. To add customizations use the hooks as described below.

/etc/rc.single

Single-user mode boots straight into the root user account and should only be used if one cannot boot normally. This script ensures no daemons are running except for the bare minimum: syslog-ng and udev. The single-user mode is useful for system recovery where preventing remote users from doing anything that might cause data loss or damage is necessary. In single-user mode, users can continue with the standard (multi-user) boot by entering 'exit' at the prompt.

/etc/rc.multi

/etc/rc.multi is run on any multi-user (i.e. normal) runlevel (i.e. 2, 3, 4, and 5). Typically, users do not notice the transition from rc.sysinit to rc.multi because rc.multi also uses /etc/rc.d/functions for handling output. This script:

1. runs sysctl to apply the settings in /etc/sysctl.conf, modifying kernel parameters at runtime; Arch has very few of these by default (mainly networking settings).
2. starts the daemons, as per the DAEMONS array in rc.conf.
3. runs /etc/rc.local to handle user customizations.

/etc/rc.local

Warning: If you have installed both of systemd and initscripts and /etc/rc.local is existent and systemd >= 197-4, system boot will not be finished, remove or rename /etc/rc.local, or uninstall initscripts to solve it.

/etc/rc.local is the local multi-user startup script. Empty by default, it is a good place to put any last-minute commands the system should run at the very end of the boot process. Most common system configuration tasks (like loading modules, changing the console font, or setting up devices) usually have a dedicated place where they are entered. To avoid confusion, ensure that commands entered in rc.local are not better suited elsewhere, such as /etc/profile.d.

When editing this file, keep in mind that it is run after the basic setup (modules/daemons), as the root user, and whether or not X starts. In this example, the rc.local script un-mutes ALSA sound settings:

/etc/rc.local

#!/bin/bash

# /etc/rc.local: Local multi-user startup script.

amixer sset 'Master Mono' 50% unmute &> /dev/null
amixer sset 'Master' 50% unmute &> /dev/null
amixer sset 'PCM' 75% unmute &> /dev/null

Custom hooks

Hooks can be used to include custom code in various places in the rc.* scripts.

Hook Name	When hook is executed
sysinit_start	At the beginning of rc.sysinit
sysinit_udevlaunched	After udev has been launched in rc.sysinit
sysinit_udevsettled	After uevents have settled in rc.sysinit
sysinit_prefsck	Before fsck is run in rc.sysinit
sysinit_postfsck	After fsck is run in rc.sysinit
sysinit_premount	Before local filesystems are mounted, but after root is mounted read-write in rc.sysinit
sysinit_end	At the end of rc.sysinit
multi_start	At the beginning of rc.multi
multi_end	At the end of rc.multi
single_start	At the beginning of rc.single
single_prekillall	Before all processes are being killed in rc.single
single_postkillall	After all processes have been killed in rc.single
single_udevlaunched	After udev has been launched in rc.single
single_udevsettled	After uevents have settled in rc.single
single_end	At the end of rc.single
shutdown_start	At the beginning of rc.shutdown
shutdown_prekillall	Before all processes are being killed in rc.shutdown
shutdown_postkillall	After all processes have been killed in rc.shutdown
shutdown_preumount	After last filesystem write (daemons have been killed), before filesystem unmount
shutdown_postumount	After filesystems have been unmounted
shutdown_poweroff	Directly before powering off in rc.shutdown

To define a hook function, create a file in /etc/rc.d/functions.d using:

function_name() {
   ...
}
add_hook hook_name function_name

Files in /etc/rc.d/functions.d are sourced by /etc/rc.d/functions. You can register multiple hook functions for the same hook, as well as registering the same hook function for multiple hooks. Don't define functions named add_hook or run_hook in these files, as they are defined in /etc/rc.d/functions.

Example

Adding the following file disables the write-back cache on a hard drive before any daemons are started (useful for drives containing MySQL InnoDB files).

/etc/rc.d/functions.d/hd_settings

hd_settings() {
    /usr/bin/hdparm -W0 /dev/sdb
}
add_hook sysinit_udevsettled hd_settings
add_hook single_udevsettled  hd_settings

First it defines the function hd_settings, and then registers it for the single_udevsettled and sysinit_udevsettled hooks. The function will be called immediately after uvents have settled in /etc/rc.d/rc.sysinit or /etc/rc.d/rc.single.

init: Login

By default, after the Arch boot scripts are completed, the /sbin/agetty program prompts users for a login name. After a login name is received, /sbin/agetty calls /bin/login to prompt for the login password.

Finally, with a successful login, the /bin/login program starts the user's default shell. The default shell and environment variables may be globally defined within /etc/profile. All variables defined by shell startup scripts within a user's home directory shall take precedence over those globally defined under /etc. For instance, if a variable is defined within both /etc/profile and ~/.bashrc, the one defined by ~/.bashrc shall prevail.

Other options include mingetty which allows for auto-login (agetty has the option to auto-login since util-linux 2.20) and rungetty which allows for auto-login and automatically running commands and programs, e.g. the always useful htop.

The majority of users wishing to start an X server during the boot process should install a display manager (see Display Manager for details).

See also

• Runlevels
• Arch Boot Process
• Linux / Unix Command: sysctl.conf
• Search the forum for rc.local examples