Creating a Launchd Plist for jackd

Moc with Homebrew

When you install moc with homebrew (brew install moc) you will see the following message:

To have launchd start jack now and restart at login:
   brew services start jack
Or, if you don't want/need a background service you can just run:
   jackd -d coreaudio

I had installed the homebrew-services tap and that integrates certain packages with launchd.

Launchd Logging

I ran the suggested command:

<> brew services start jack
==> Successfully started `jack` (label: homebrew.mxcl.jack)

But it wasn’t actually running:

<> ps -ef | grep jack
1000 11364 10834   0  5:24PM ttys007    0:00.00 grep --color=auto jack

In the logs I just saw this:

<> tail -f /var/log/system.log
Oct  8 11:04:45 macair com.apple.xpc.launchd[1] (homebrew.mxcl.jack): This service is defined to be constantly running and is inherently inefficient.
Oct  8 11:04:45 macair com.apple.xpc.launchd[1] (homebrew.mxcl.jack): Service only ran for 0 seconds. Pushing respawn out by 10 seconds.
Oct  8 11:04:55 macair com.apple.xpc.launchd[1] (homebrew.mxcl.jack): Service only ran for 0 seconds. Pushing respawn out by 10 seconds.
Oct  8 11:05:05 macair com.apple.xpc.launchd[1] (homebrew.mxcl.jack): Service only ran for 0 seconds. Pushing respawn out by 10 seconds.

It wasn’t very helpful. I then ran into MOC on OS X which had the manual steps on how to create the service. So I removed the one from the homebrew:

<> brew services stop jack
Stopping `jack`... (might take a while)
==> Successfully stopped `jack` (label: homebrew.mxcl.jack)

And started troubleshooting it manually. First I ran into Logging with Launchd and that had instructions on how to add some logging outputs. So with that information, I created the following plist:

<> cat Library/LaunchAgents/org.jackaudio.jackd.plist
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
  <key>EnvironmentVariables</key>
  <key>Label</key>
  <string>org.jackaudio.jackd</string>
  <key>WorkingDirectory</key>
  <string>/usr/local/Cellar/jack/0.125.0_1</string>
  <key>ProgramArguments</key>
  <array>
    <string>/usr/local/bin/jackd</string>
    <string>-v</string>
    <string>-d</string>
    <string>coreaudio</string>
  </array>
  <key>StandardOutPath</key>
  <string>/usr/local/var/log/jackd.log</string>
  <key>StandardErrorPath</key>
  <string>/usr/local/var/log/jackd-error.log</string>
  <key>RunAtLoad</key>
  <true/>
  <key>KeepAlive</key>
  <true/>
</dict>
</plist>

I also added -v arguement to the jackd command to see more information. Then I loaded the script:

<> launchctl load -w ~/Library/LaunchAgents/org.jackaudio.jackd.plist

And in the logs I saw the following:

<> tail /usr/local/var/log/jackd.log
jackd 0.125.0
Copyright 2001-2009 Paul Davis, Stephane Letz, Jack O'Quinn, Torben Hohn and others.
jackd comes with ABSOLUTELY NO WARRANTY
This is free software, and you are welcome to redistribute it
under certain conditions; see the file COPYING for details

getting driver descriptor from /usr/local/Cellar/jack/0.125.0_1/lib/jack/jack_dummy.so
getting driver descriptor from /usr/local/Cellar/jack/0.125.0_1/lib/jack/jack_coreaudio.so
getting driver descriptor from /usr/local/Cellar/jack/0.125.0_1/lib/jack/jack_net.so
JACK compiled with POSIX SHM support.
registered builtin port type 32 bit float mono audio
registered builtin port type 8 bit raw midi

And this:

<> tail /usr/local/var/log/jackd-error.log
Unable to get tmpdir in user dir
Unable to get tmpdir in engine
cannot create server sockets
cannot create engine

And also this:

<> tail -f /var/log/system.log
Oct  8 17:04:13 macair com.apple.xpc.launchd[1] (org.jackaudio.jackd[9491]): Service could not initialize: 17A: xpcproxy + 11572 [1522][43FABD]: 0x2
Oct  8 17:04:13 macair com.apple.xpc.launchd[1] (org.jackaudio.jackd): Service only ran for 0 seconds. Pushing respawn out by 10 seconds.

Environment Variables with Launchd

Then I ran into PATCH: use a fixed jackd path for tmpdir query, and from that page, it seems that the PATH variable wasn’t set right and jackd couldn’t be found to run jackd -l, which shows where the tmp directory is:

<> /usr/local/bin/jackd -l
/tmp

So then I ran into Use an environment variable in a launchd script and there was an example on how to set environment variables in launchd plist files. So after that I created the following plist:

<> cat Library/LaunchAgents/org.jackaudio.jackd.plist
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
  <key>EnvironmentVariables</key>
  <dict>
         <key>TMPDIR</key>
         <string>/tmp</string>
         <key>PATH</key>
         <string>/usr/local/bin</string>
  </dict>
  <key>Label</key>
  <string>org.jackaudio.jackd</string>
  <key>WorkingDirectory</key>
  <string>/usr/local/Cellar/jack/0.125.0_1</string>
  <key>ProgramArguments</key>
  <array>
    <string>/usr/local/bin/jackd</string>
    <string>-d</string>
    <string>coreaudio</string>
  </array>
  <key>StandardOutPath</key>
  <string>/usr/local/var/log/jackd.log</string>
  <key>StandardErrorPath</key>
  <string>/usr/local/var/log/jackd-error.log</string>
  <key>RunAtLoad</key>
  <true/>
  <key>KeepAlive</key>
  <true/>
</dict>
</plist>

Then I reloaded the script:

<> launchctl unload -w ~/Library/LaunchAgents/org.jackaudio.jackd.plist
<> launchctl load -w ~/Library/LaunchAgents/org.jackaudio.jackd.plist

And then jackd was running:

<> ps -ef | grep jack
1000 10763     1   0  5:15PM ??         0:27.48 /usr/local/bin/jackd -d coreaudio
1000 11717  4885   0  5:39PM ttys003    0:00.00 grep --color=auto jack

You can confirm the environment variables set for a launchd script by running the following:

<> launchctl print gui/1000/org.jackaudio.jackd
org.jackaudio.jackd = {
    active count = 3
    path = /Users/elatov/Library/LaunchAgents/org.jackaudio.jackd.plist
    state = running

    program = /usr/local/bin/jackd
    arguments = {
            /usr/local/bin/jackd
            -d
            coreaudio
    }

    working directory = /usr/local/Cellar/jack/0.125.0_1

    stdout path = /usr/local/var/log/jackd.log
    stderr path = /usr/local/var/log/jackd-error.log
    inherited environment = {
            Apple_PubSub_Socket_Render => /private/tmp/com.apple.launchd.lIHQklt3qF/Render
            SSH_AUTH_SOCK => /private/tmp/com.apple.launchd.VL11NowySr/Listeners
    }

    default environment = {
            PATH => /usr/bin:/bin:/usr/sbin:/sbin
    }

    environment = {
            PATH => /usr/local/bin
            TMPDIR => /tmp
            XPC_SERVICE_NAME => org.jackaudio.jackd
    }

I left the logging on just in case I will need to troubleshoot later, and after it was working I just saw this in the logs:

<> tail /usr/local/var/log/jackd-error.log
server `default' registered
Error calling AudioUnitSetProperty - kAudioUnitProperty_StreamFormat kAudioUnitScope_Output
poll failed (Bad file descriptor)
cleaning up shared memory
cleaning up files
unregistering server `default'
Error calling AudioUnitSetProperty - kAudioUnitProperty_StreamFormat kAudioUnitScope_Output

Which is what I would see when I would run the command manually in my terminal.