compatd

A lightweight systemd compatibility layer for OpenRC-based Linux distributions.

Designed for OpenRC-based distributions such as Artix, Gentoo and Alpine Linux.

Why?

Some packages ship .service files and assume systemd. On OpenRC you can either:

• Write init scripts by hand (tedious)
• Convert automatically with compatd
• Run the LD_PRELOAD shim if a binary calls sd_journal_* / sd_notify

Features

• systemctl-compatible wrapper — preserves muscle memory: start, stop, enable, disable, status, is-active, is-enabled, daemon-reload, list-units, cat, poweroff, reboot, hibernate
• Convert units — .service → OpenRC, .timer → cron, .socket → s6, .mount → fstab
• LD_PRELOAD shim — minimal implementations of sd_notify, sd_journal_*, sd_booted, sd_listen_fds, sd_watchdog_enabled, sd_id128_get_machine for software that calls systemd APIs directly
• Socket activation — fd-passing for -H fd:// style services
• Cgroup delegation — handles Delegate=yes via cgroup v2
• Pacman hook — converts new .service files automatically after package install
• elogind integration — seamless compatibility through libelogind

Usage

Convert units

# .service → OpenRC
compatd convert service /usr/lib/systemd/system/docker.service > /etc/init.d/docker
chmod +x /etc/init.d/docker
rc-update add docker default

# .timer → cron
compatd convert timer /usr/lib/systemd/system/daily-cleanup.timer >> /var/spool/cron/root

# .socket → s6
compatd convert socket /usr/lib/systemd/system/docker.socket > /etc/s6/docker/run

# .mount → fstab
compatd convert mount /usr/lib/systemd/system/var-data.mount >> /etc/fstab

systemctl wrapper

systemctl start docker
systemctl enable docker
systemctl status docker
systemctl is-active docker
systemctl is-enabled docker
systemctl daemon-reload
systemctl list-units
systemctl cat docker
systemctl poweroff
systemctl reboot
systemctl hibernate

Socket activation

compatd socket-activate --listen-stream /run/docker.sock -- dockerd -H fd://

Installation

# Build from source (PKGBUILD, Artix/Arch)
git clone https://github.com/DipCrai/compatd
cd compatd && makepkg -si

# Build with Cargo (any distribution)
cargo build --release

# Local install script
./install.sh

How it works

1. Unit parser — custom parser for .service / .timer / .socket / .mount (no external dependencies)
2. Unit converter — translates parsed units to OpenRC, cron, s6, fstab
3. LD_PRELOAD shim (libcompatd_preload.so) — provides minimal implementations for sd_notify, sd_journal_*, sd_booted, sd_is_socket, sd_listen_fds, sd_watchdog_enabled, sd_id128_get_machine; journal writes go to syslog(3), reads return empty
4. systemctl wrapper — maps 11 systemctl commands to rc-service / rc-update / compatd
5. Pacman hook — post-transaction script converts newly installed .service files
6. elogind — drop-in replacement for libsystemd where applicable

Limitations

compatd handles the most common unit patterns. Complex features may need manual adjustments:

• Socket activation internals (fd-passing works, but full socket unit lifecycle isn't replicated)
• Transient units (dynamically created by systemd at runtime)
• Advanced cgroup configuration beyond Delegate=yes
• systemd generators and portable services
• .path / .slice / .scope unit types

If you hit something that doesn't convert cleanly, open an issue.