As of August 20th, 2015, the steps in this guide still work on up-to-date installations of Arch Linux. However, it isn't going to be updated any further. I'm leaving it up because some people may still find it to be a valuable resource, but you probably shouldn't rely entirely on the steps here.
An easier, more comprehensive guide can be found here: http://systemd-free.org/.
Whether you appreciate the superior system administration capabilities of OpenRC, want to reduce boot time, or simply hate systemd, there are plenty of reasons to want to change your init system. This guide will walk you through doing it in what I have found to be the most reliable way.
You need to install a bunch of AUR packages to get OpenRC working on Arch. For various reasons, many of them can't be installed with yaourt. I'll note when a package can be installed with yaourt. I recommend using yaourt whenever possible, as its automatic dependency handling is really convenient. If you're unfamiliar with yaourt, look at https://wiki.archlinux.org/index.php/Yaourt.
For the sake of completeness, instructions to install a package from the AUR can be found here: https://wiki.archlinux.org/index.php?title=Arch_User_Repository.
The first step is to install SysVinit. I know what you're thinking: isn't this a guide about installing OpenRC, a different init system? Well, OpenRC runs on top of SysVinit. In this configuration, all SysVinit does is launch OpenRC and then take PID 1. This way, the init service manager and PID 1 are separated, so if your init system goes down, the system can still stay alive.
To install SysVinit, just install the AUR package sysvinit. This can be done with yaourt.
To install OpenRC, get the package openrc-core. This can be done using yaourt. There are several other OpenRC packages in the AUR. Those will not work with this method.
There are three package bases containing init scripts for OpenRC. I recommend having all three built and installing the packages they contain as needed. The package bases are openrc-base, openrc-desktop, and openrc-misc.
At the time of writing, openrc-base and openrc-misc have broken PKGBUILD files. Patched versions are included in this repository. To use the patched version, replace the PKGBUILD file in the package base with the one from this repository before running makepkg.
To build a package base, download and extract its archive, replace the PKGBUILD file if necessary, and then run makepkg from the directory of the PKGBUILD. This should build several packages in that directory. You should install the packages for any init services you want. For instance, if you want to use ntp, then install the ntp-openrc package from the openrc-misc base.
When you install a package, it will tell you how to enable it.
To enable a service in OpenRC, use
# rc-update add <service-name> <runlevel>
Where runlevel is the name of the runlevel, not it's number. For our purposes, we'll be using the runlevel default.
You can start and stop services using
# rc-service <service-name> [<command>]
Where command is something like start, stop, restart, etc. Run it with no command to see the list of available commands.
To see all enabled services, do
$ rc-update show [<runlevel>]
Finally, to see all of the services you have available, do
$ ls /etc/init.d
Check out the man pages and the internet for more information.
You need to have a logging daemon installed. If you don't already have one, I recommend syslog-ng from the official Arch repositories. It has a service written for it available in openrc-base. Enable it with
# rc-update add syslog-ng default
You probably want a cron daemon. cronie is a good choice that is available from the official repositories and has its service available in the openrc-base package base. Enable it with
# rc-update add cronie default
Everything these days needs dbus. Install the dbus-openrc package from openrc-base and enable it with
# rc-update add dbus default
If you want sound, you should add the ALSA service. It is available in the package alsa-utils-openrc from the openrc-desktop package base. After it's installed, enable it with
# rc-update add alsasound default
Install acpid-openrc from openrc-misc, and run
# rc-update add acpid default
Ah, network configuration, the most fun part of setting up any init system. If you use DHCP, then you should enable the dhcpcd service, which is available in openrc-base. There are also services for NetworkManager and wicd if you want to use either of those.
To set up static routing, you need to edit the /etc/conf.d/net file. The file is well-documented and should tell you everything you need to know. After editing this file, to enable your interface, you need to make a symlink to /etc/init.d/net.lo and enable that. For example, if you want to enable an interface named eno1, you would do:
# ln -s /etc/init.d/net.lo /etc/init.d/net.eno1
# rc-update add net.eno1 default
There is also a service for wpa-supplicant if you want to automatically connect to a wireless network, but I recommend using NetworkManager or wicd instead.
If you use NetworkManager, you'll need to build and install networkmanager-consolekit from the AUR. You can use yaourt for this. You'll also need consolekit, so look at the section "Installing consolekit" below.
When you install the networkmanager-openrc package, it will complain that there is no service named "networkmanager". This is quite alright. Just run
# rc-update add NetworkManager default
to enable the service.
Hostname configuration is done through the file /etc/conf.d/hostname. Put this line into the file:
HOSTNAME=darkstar
Where "darkstar" is replaced by whatever you want your hostname to be.
You should enable avahi. Install avahi-openrc from openrc-desktop and run
# rc-update add avahi default
To enable audio, simply add your user to the audio group.
# usermod <user> -aG audio
Arch uses logind to provide rootless X. Since logind only works when systemd has PID 1, we need to make some changes so that users can run X. Edit the file /etc/X11/Xwrapper.config so that it contains line:
need_root_rights=yes
Confusingly enough, this makes it so users other than root can start X. If you're curious about how this works, check out the man page for Xorg.wrap(1).
Also be sure to get DRI working if you want accelerated graphics.
In order to access DRI devices, a user needs to be a member of the video group. Add your user like this:
# usermod <user> -aG video
consolekit is a very important piece of software that was replaced by logind. However, now that we've nixed systemd, we want consolekit back. Install it with the consolekit package from the AUR.
While you're at it, I also recommend installing polkit-consolekit. As well as installing and enabling the consolekit-openrc service from the openrc-desktop package base.
Mercifully, this can all be done using yaourt.
DEs and DMs tend to rely on logind, which, as we said before, doesn't work anymore. For information about getting specific DEs and DMs working, check out https://wiki.archlinux.org/index.php/Openrc#Using_OpenRC_with_a_desktop_environment.
You'll probably need to install consolekit from the AUR.
At this point, you should be able to reboot your system and have it work. If for some reason, it doesn't, then use your bootloader to add this to your kernel parameters
init=/usr/lib/systemd/systemd
This will start the system with systemd as init, allowing you to go in and examine your system to see what went wrong.
If you have any problems, check out https://wiki.manjaro.org/index.php?title=OpenRC,_an_alternative_to_systemd and https://wiki.parabola.nu/OpenRC. These wiki articles don't apply perfectly to Arch, but since both Manjaro and Parabola are based on Arch, they should be quite helpful.
Technically, you can skip this step. However, by following through with it, you can save some disk space and show Poettering that you mean business.
Make sure you test your system by rebooting before you remove systemd. If OpenRC doesn't work, then you'll have to fix your system with a recovery disk, which is never fun.
With OpenRC and SysVinit installed, systemd's one remaining job is to provide udev. In order to finally slay Goliath, we need to replace it with something else. eudev is a udev fork from Gentoo which works nicely with OpenRC.
Installing eudev is a pain in the ass because it conflicts with systemd, so you get some weird dependency issues. In order to do it, first download eudev and eudev-systemdcompat from the AUR and unpack them.
$ tar xzf eudev.tar-gz
$ tar xzf eudev-systemdcompat.tar.gz
Install some dependencies:
# pacman -S glib2 kbd kmod hwids util-linux gobject-introspection gperf \
gtk-doc intltool libgcrypt xz
Next, we want to build both packages. We can't install them yet, because of dependency issues. Since eudev-systemdcompat depends on eudev, we run makepkg with the -d flag to ignore dependencies.
$ cd eudev
$ makepkg
$ cd ../eudev-systemdcompat
$ makepkg -d
$ cd ..
Finally, install both packages at the same time, removing systemd when prompted.
# pacman -U eudev/eudev*.pkg.tar.xz eudev-systemdcompat/eudev-systemdcompat.*.pkg.tar.xz
Depending on your system, you may also want to install libsystemd-standalone to provide some of the other libraries from systemd.
After installing eudev, network interface names may change. This is most important if you're using a wireless adapter, because the name will change from something like wlp1s0 to something like wlan0. To see the available network interfaces, do:
$ ls /sys/class/net
At this point, you have a fast, OpenRC-based, systemd-free init. Congratulations! Here are a few more things you can do from here.
You may have some weird boot errors about missing configuration files for sysctl or tmpfiles.d. These are annoying because they slow down the boot process substantially. You can fix these errors by running:
# sudo touch /etc/sysctl.conf /usr/lib/tmpfiles.d/tmp.conf /usr/lib/tmpfiles.d/var.conf
If you want a blazing fast boot, you can enable parallel initialization for OpenRC. You can get it by adding this line to the file /etc/rc.conf
rc_parallel="YES"
Disclaimer: This is still an experimental feature and may break your init (but it probably won't).
OpenRC is a powerful system administration tool, so take full advantage of it by adding more runlevels. For instance, you can have single-user recovery modes, runlevels without networking, one that starts a display manager, and so on.
Browse through the available services in the three script package bases we built as a good starting point. It's also easy to write your own services if you're familiar with bash.
The man pages for OpenRC and its tools are really helpful. Check them out.
Also, there's a whole internet out there. Look at the wiki pages linked in the Troubleshooting section for some good starting points.
If there are any problems with this guide, please open an issue. Feel free to rehost it wherever you want; after all, we need to save as many people as possible from systemd. Finally, if you have any suggestions to clarify or improve this guide, please open a pull request.