launchd HOWTO

MacOS X 10.5 has autofs, but 10.4 doesn’t. Alternative solution is am-utils, available in MacPorts. However, MacPorts doesn’t provide any way to launch amd at startup.

In MacOS X, there’s no scripts like /etc/rc, but there’s launchd. I spent about a half day to launch amd by launchd and learned:

• Write the policy to launch in /System/Library/LaunchDaemons/foobar.plist
• The process spawned by foobar.plist must NOT go background, but must stay in foreground (see launchd.plist(5)!).

However, my sweet amd goes background… So, launchd misunderstands: “Oh, amd is dead. I must start a new one!” and there will be so many amd processes.

As the solution, I wrote a simple wrapper script (amd_start) like:

#!/bin/sh
/opt/local/sbin/amd -F /opt/local/etc/amd.conf
while [ true ]; do
sleep 360000
done

And my amd.plist is this:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple Computer//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
<key>Label</key>
<string>amd</string>
<key>OnDemand</key>
<false/>
<key>ProgramArguments</key>
<array>
<string>/System/Library/amd_start</string>
</array>
<key>ServiceIPC</key>
<false/>
</dict>
</plist>

Put this in /System/Library/LaunchDaemons/amd.plist, then:

% sudo launchctl load /System/Library/LaunchDaemons/amd.plist

This will launch amd.

launchd is fun… It works as /etc/rc, crond and inetd. Wow.