Systemd compatibility for SysV systems

Overview

This set of tools allow Systemd services to run unmodified on SysV-style systems. It consists of two programs:

• systemctl provides a subset of the functionality of Systemd's systemctl; specifically, most of the service-related commands.
• sysvrun launches and monitors a Systemd service, providing restart functionality which a SysV-style init is not capable of.

In addition, a mock daemon, mockd, is provided for test purposes.

NOTE: this software is not compatible with Linux kernels older than 2.6.27.

Building

sysvkit uses [SCons][] and pkg-config for building.

Before building sysvkit for the first time, run

git submodule update --init

To build sysvkit, run

scons [ prefix=<prefix> ]

from the top-level sysvkit directory. The optional prefix argument is a directory, /usr/local by default, where the build system installs sysvkit.

To install sysvkit, run

sudo scons [ prefix=<prefix> ] install

Model

Services

For the purposes of these tools, a service is represented by a script in /etc/init.d. The service name is the name of the script, not the Provides line in the LSB comment block. For interoperability, any .service suffix will be stripped from the name passed on the command line before looking for the script, so

systemctl enable my.service

and

systemctl enable my

are equivalent, provided /etc/init.d/my exists.

A service is considered to be enabled if links to it exist in at least one of the rc directories for runlevels 2 through 5. Enabling a service creates links for all four runlevels, and disabling a service deletes them.

The state of a service is determined by invoking its init script's status command and interpreting its exit code as described in the Linux Standard Base Core Specification, cf. LSB 5.0.0 section 22.2.

Launcher

The launcher, sysvrun, is intended to be invoked from an init script, but can just as easily be run from the command line. It reads a Systemd unit file describing a service and performs the requested command (start, stop, reload, status). If the service does not daemonize itself, sysvrun will do so; and if it requires monitoring, sysvrun will monitor and restart it if necessary.