ecliptik/docker-cron-container-starter repository overview

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A version for the Raspberry Pi⁠

⁠Cron Container Starter

This is a simple Docker image that starts local Docker containers based on a cron schedule.

This is based off sillelien/tutum-cron⁠ which does the same job but inside Tutum.

⁠Why would I want this?

This is quite useful to run backups or other scheduled jobs. Rather than having each of these jobs in a container with their own cron schedules, you can use this image to keep all schedule job configuration in one place.

⁠How does it work?

The Docker socket must be provided to the container as a volume at /var/run/docker.sock. Through this, the container can issue a start command.

fcron is used to schedule this API call.

⁠Building

Pull the repository and run: docker build -t jordancrawford/cron-container-starter ..

⁠Running

To run you must:

• provide /var/run/docker.sock as a volume
• provide your cron schedules as environment variables. These must be of the format: CONTAINER_<container name to start>=<cron schedule>

⁠Cron Schedules

See the fcron documentation⁠ or crontab-generator⁠ for help.

⁠Docker Compose

The easiest way to run the image is within Docker Compose. Below an example Docker Compose file that runs a test container every minute.

cron-container-starter:
   container_name: cron-container-starter
   image: jordancrawford/cron-container-starter
   restart: always
   # Don't take a large portion of memory or CPU shares.
   cpu_shares: 128
   mem_limit: 64m
   # Setup container start rules.
   environment:
    CONTAINER_test: '* * * * *'
   # Setup the Docker socket as a volume so the container can control Docker.
   volumes:
    - /var/run/docker.sock:/var/run/docker.sock
test:
   image: alpine
   container_name: test
   command: 'echo On Schedule'