boxinit is a small program with init-like capabilities and is intended to be run as PID-1 process inside docker containers.
Features:
- relay signals to child processes: INT, HUP, TERM, QUIT, USR1, USR2
- run a couple of child processes and exit if any of them returns, terminating all other children
- adopt orphaned processes and reap them when they finish (solve zombie processes issue)
boxinit takes arbitrary number of arguments each of them treated as a name of the command to run (without parameters). Use wrapper scripts and environment variables if you need to configure complex start commands.
Example:
Consider you want to run two services inside your container and finish container if any of those two services terminates.
Create start script for each service holding configuration parameters, etc:
cat service1.sh
#!/bin/sh
exec /usr/bin/my-service1 --config=/etc/service1.conf
cat service2.sh
#!/bin/sh
exec /usr/bin/my-service2 --foo=bar
Configure your Dockerfile as following:
COPY service*.sh boxinit /init/
CMD [ "/init/boxinit", "/init/service1.sh", "/init/service2.sh" ]
This way boxinit would be your PID-1 process inside container, would relay essential signals to both services and would exit if either of them finish, allowing you to restart/heal container.