Docker for Mac Beta is very nice – more integrated with OS X and significantly faster. The only issue I have encountered so far is the Docker API not being available over HTTP.
The problem can be overcome using socat and launchd; socat is used to expose a HTTP endpoint on which the Docker API is available and launchd to automatically start the socat forwarder each time OS X is started. The socat workaround has been suggested by several persons – thanks! My own laziness drove me to create the launch daemon job.
The most convenient way to install socat is using Homebrew:
- If you haven’t installed Homebrew, do it using the following command in a terminal window:
/usr/bin/ruby -e "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/master/install)"
- Install socat:
brew install socat
If you now try the socat command without any parameters in the terminal, you should see output similar to this:
2016/05/21 11:43:41 socat E exactly 2 addresses required (there are 0); use option "-h" for help
Create a Launch Daemon
Some research told me that creating a launch daemon is the appropriate way to run a script or program at startup. Further details are available here.
After some tinkering, I came up with the following launchd job configuration:
<?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>Label</key> <string>se.ivankrizsan.socat_launcher</string> <key>Disabled</key> <false/> <key>RunAtLoad</key> <true/> <key>KeepAlive</key> <true/> <key>ProgramArguments</key> <array> <string>/usr/local/bin/socat</string> <string>-d</string> <string>TCP-LISTEN:2376,range=127.0.0.1/32,reuseaddr,fork</string> <string>UNIX:/var/run/docker.sock</string> </array> <key>StandardErrorPath</key> <string>/Library/Logs/socat_docker.log</string> <key>StandardOutPath</key> <string>/Library/Logs/socat_docker.log</string> <key>StartInterval</key> <integer>30</integer> </dict> </plist>
- The value of the “Label” key must be unique among your launchd jobs.
- The launchd job can be disabled by setting the key “Disabled” value to true.
- The launchd job will be run at startup (RunAtLoad) and restarted if the process is terminated (KeepAlive).
- The program to execute is the first value in array of the “ProgramArguments” key.
- The arguments to socat needs to have one <string> elements each in the program arguments array.
- The Docker API HTTP endpoint will be made available on port 2376.
In addition, the Docker API HTTP endpoint will only be available from localhost (range=127.0.0.1/32).
If you want to open the Docker API HTTP endpoint to access from any IP, modify row 17 of the launchd job configuration to look like this:
- Log from socat will be written to the file /Library/Logs/socat_docker.log
- Socat will be restarted with a 30 second interval if needed (StartInterval).
To activate the launchd job configuration:
- Save the above launchd job configuration to a file with the postfix “.plist” (without quotes).
My file is named “se.ivankrizsan.socat_launcher.plist”.
- Copy the file you just saved to /Library/LaunchDaemons on your OS X boot disk.
- Open a terminal window.
- Go to the launch daemons directory:
- Set the owner and group of the new launchd job configuration file:
sudo chown root:wheel se.ivankrizsan.socat_launcher.plist
- Load the launchd job configuration.
This can be accomplished either by rebooting OS X or by the following command in the terminal:
sudo launchctl load se.ivankrizsan.socat_launcher.plist
- Open the Console application and examine the system log for entries related to socat and the socat_docker.log log file.
- Start the Docker (for Mac Beta) application.
- Open the link http://127.0.0.1:2376/version in a browser.
You should see output similar to this:
If there are problems regarding the permissions of the launchd job configuration file, use Disk Utility to repair permissions as a last resort.