Comitup and Docker - Tutorial

[davesteele]

So, Comitup routinely modifes network interface states and configurations, and insists on owning port 80 at least some of the time. These things can affect the healthy life-cycle of a typical Docker container. Here is a way to work around the problem by running the container only when Comitup is in the CONNECTED state

Start with a Pi running a Comitup Image, and connect to an upstream Access Point.

Install docker.

Let's run a simple demonstration web-serving container, borrowed from this article. Call it demo:

docker run -d -p 80:80 -name demo hypriot/rpi-busybox-httpd

Edit /etc/comitup.conf to enable the state change callback:

# An external script that is called on comitup state changes. It will
# include a single argument, either 'HOTSPOT', 'CONNECTING', or
# 'CONNECTED'.
#
# The script must be executable. It will be run with the permissions of the 
# owning user.
#
external_callback: /usr/local/bin/comitup-callback

Create and configure the docker control script:

# cat /usr/local/bin/comitup-callback
#!/usr/bin/bash

if [ $1 == "CONNECTED" ] ; then
  docker start demo
else
  if [ $1 == "HOTSPOT" ] ; then
    docker stop demo
  fi
fi

# chmod 755 /usr/local/bin/comitup-callback
# chown root.root /usr/local/bin/comitup-callback

Reboot the Pi. The demo website should be accessible when the device is CONNECTED.

[davesteele]

Note that, when in appliance mode, the upstream connection is NAT'd, which can interfere with inbound connections.