Arch Linux Init System Decision Guide: Comparing systemd, OpenRC, and runit

Arch Linux Init System Decision Guide: Comparing systemd, OpenRC, and runit

The init system is PID 1—the first process the kernel starts. On Arch Linux it controls service startup, dependency ordering, and session management. The default is systemd, but OpenRC and runit are available alternatives. Choosing between them is a trade-off between integration, simplicity, and resource use.

Takeaway: Keep systemd unless you have a specific constraint that rules it out. If you switch to OpenRC or runit, expect to write service definitions manually, replace systemd-specific components, and validate the change on a non-production system first.

Decision constraints

Before comparing options, identify your constraints. Rolling-release Arch updates init packages frequently, so any non-default configuration must be maintained across upgrades. If your workload depends on systemd-specific APIs such as journald or logind, switching will require replacements like elogind. Production systems should be tested on a spare machine or VM first.

Supported options compared

Init System	Dependency Handling	Resource Footprint	Package Source	Best Fit
systemd	Full dependency graph, socket activation, timers	Moderate to high (multiple resident daemons)	Official repositories; default	Desktops and servers needing journald, logind, and tight integration
OpenRC	POSIX shell scripts with explicit start/stop ordering	Low (no background daemon)	AUR (e.g., openrc, openrc-arch-services-git)	Minimalist installs, learning init internals, avoiding systemd
runit	Minimal supervision; no built-in dependency resolution	Very low	Official repositories (runit)	Containers, embedded targets, fastest boot scenarios

Trade-offs

systemd offers the richest feature set and is the only init fully supported by Arch's default installation scripts. Its socket activation can reduce idle processes, but the dependency graph and multiple daemons add complexity. OpenRC trades advanced dependency resolution for transparency: service scripts are plain shell files you can read and edit. The risk is that omitted dependencies can cause race conditions at boot. runit is the smallest and fastest, yet you must write service definitions and ordering yourself, which increases the chance of misconfiguration for common services like SSH or NTP.

Implementation: switching to OpenRC

The following path is conservative and assumes you have a backup or snapshot. OpenRC is not enabled by default, and removing systemd can break packages that depend on it. Test in a VM first.

1. Update and snapshot. Run sudo pacman -Syu and ensure you have a rollback plan (btrfs snapshot, disk image, or live USB).
2. Install OpenRC and Arch service scripts. Using an AUR helper, install openrc and openrc-arch-services-git. These provide the init binaries and Arch-specific service definitions in /etc/init.d.
3. Replace systemd session management. Install elogind to provide a logind-compatible library for desktop sessions without the systemd daemon.
4. Remove systemd. Run sudo pacman -Rsn systemd systemd-sysvcompat. Pacman will list dependent packages; remove or replace them as needed. This step can be large on desktop systems.
5. Regenerate boot artifacts. If you use GRUB, run sudo grub-mkconfig -o /boot/grub/grub.cfg. Regenerate the initramfs with sudo mkinitcpio -P.
6. Reboot and verify PID 1. After reboot, run ps -p 1 -o comm=. The output should no longer be systemd; it should reflect your new init (for example, openrc-init or init depending on the OpenRC build).

Validation and rollback

After the system boots, list services with rc-status --servicelist and check critical daemons individually, for example rc-service sshd status. Review boot logs in /var/log/boot.log for missing dependencies. If the system fails to boot, boot an Arch live USB, mount the root filesystem, chroot into it, reinstall systemd with pacman -S systemd, restore your bootloader configuration, and reboot.

Limitations: Some AUR packages assume systemd and may lack OpenRC service files. Hardware enablement that relies on udev rules from systemd may need eudev or manual adjustment. Because Arch is rolling-release, verify package names and dependency chains against current repositories before switching.