csjayp / relaunchd

A service management daemon similar to launchd(8)

relaunchd

Overview

relaunchd is a service management daemon that is similar to the launchd(8) facility found in the Darwin operating environment [1].

It was written from scratch based on the published API, and all code is available under the ISC license. See the LICENSE file for more information.

It is currently under heavy development, and should not be used for anything important. Be especially mindful that there is NO WARRANTY provided with this software.

Status

relaunchd is primarily developed on FreeBSD, but it compiles under Linux and should work there as well.

The core functionality is working:

• loading and unloading jobs with launchctl
• launching jobs
• socket-activated jobs via the Sockets key
• periodic jobs that use the StartInterval key

There are some new features not found in the original launchd:

• JSON is used instead of XML
• you can launch programs that place themselves inside of a jail(8)
• a wrapper library that allows programs to use socket activation without modifying the source code.

Some things are not implemented yet:

• cron emulation via the StartCalendarInterval key
• file and directory watches - WatchPaths, QueueDirectories
• restarting jobs if they crash - TimeOut, ExitTimeout, KeepAliveTimeout, ThrottleInterval
• resource limits - SoftResourceLimits, HardResourceLimits
• miscellaneous - LaunchOnlyOnce, inetdCompatibility, EnableGlobbing, RunAtLoad, Umask

Some things will probably never be implemented:

• oddities - LimitLoadToHosts, LimitLoadFromHosts
• kernel and launchd debugging - Debug, WaitForDebugger
• Mach IPC
• the StartOnMount key - may require kernel support for filesystem mount notifications
• the original XML plist format; use JSON instead.
• hacks and workarounds - HopefullyExitsFirst, HopefullyExitsLast
• Darwin-specific things - EnableTransactions
• legacy keys - Disabled, OnDemand

Building (all platforms)

The basic commands to build and install the software are:

	make
	sudo make install

Building under Linux

You can check the current build status by visiting the Travis CI dashboard

There are a few extra steps when building on Linux:

1. Download and install libkqueue. For Debian-based distributions, you can simply run:

   sudo apt-get install libkqueue-dev

   Other distributions will require you to build from source, which is available at:

   https://github.com/mheily/libkqueue/

Socket activation

relaunchd uses a different mechanism for socket activation than the one that Darwin uses.

TODO -- document this

Installation

Currently, relaunchd has only been tested on FreeBSD 10, but should be portable to other BSD operating systems.

To install relaunchd, run the following commands:

make
sudo make install

This will install the following executable commands:

• launchd
• launchctl

It will also install the following manpages:

• launchctl(1)
• launchd(8)
• launchd.plist(5)

Usage

To start launchd, run the following command:

/usr/local/sbin/launchd

If you want to run jobs as your own user account, add the following line to your .xinitrc file:

/usr/local/sbin/launchd

If you don't have an .xinitrc file, refer to the documentation for your desktop environment to determine the best way to automatically execute a command when you login.

Differences with Darwin launchd

There are some specific design choices that make relaunchd different from the or iginal launchd found in Darwin.

The original launchd uses friendly MacOS-style names for the directories where its configuration files are stored. For example, one of the directories is named /System/Library/LaunchDaemons. Relaunchd uses more traditional lowercase names, and stores it's files in:

$HOME/.launchd/agents
/usr/local/etc/launchd/agents
/usr/local/etc/launchd/daemons
    /usr/local/share/launchd/daemons
    /usr/local/share/launchd/agents

On FreeBSD, there is no compelling reason to have launchd run as pid #1, so relaunchd is designed to be started by the traditional init(8) command. Relaunchd currently coexists with the /etc/rc mechanism, until such time as all of the /etc/rc.d scripts can be converted to launchd jobs.

Instead of using the XML plist format, job manifests are specified using JSON.

In the Darwin implementation, there is a single launchd(8) process that is accessible to all user accounts. In relaunchd, there is a "system launchd" process that runs as root and is not accessible by unprivileged users. Each unprivileged user may run their own launchd process under their own UID.

Contact Information

For questions, comments, or other feedback about relaunchd, you can send an email to the author at:

Mark Heily <[email protected]>

There is also a #relaunchd IRC channel on FreeNode. If you don't have an IRC client, there is a web-based chat client available.

References

[1] https://developer.apple.com/library/mac/documentation/Darwin/Reference/ManPages/man8/launchd.8.html