runc-demo

This is a simple little project to play around with kicking off a container using runc on a host from an init-container.

init-container

The init-container is our transport/install mechanism for our runc image. The entrypoint for this container will kick off the init-script which will copy the rootfs directory and our runc binary on to the host node. We'll also copy in a systemd file to use to control our service.

runc image

We're using a simple image to demo runc here, it really doesn't do much; just launches an Alpine container via runc which is set up to print a simple message out to /tmp/demo.out on the host node every 5 seconds.

Trying things out

Set an environment variable to point to specify an image tag and be able to push it to your registry (TODO: enable quay options)

make image

Will build our runc-demo container image (just your usual docker build type of thing here), by default it's tag is jgriffith/runc-demo.

make run

Will launch the runc-demo container we built, the init containers entrypoint will run a simple script to copy all of our files to the host machine including a systemd file; and then will try and kick off the runc container using systemd. After the init-container runs you should expect to see the runcdemo service running on the host machine:

"""

ubuntu@uplifting-chihuahua:~$ sudo systemctl status runcdemo ● runcdemo.service - runc demo Loaded: loaded (/etc/systemd/system/runcdemo.service; enabled; vendor preset: enabled) Active: active (exited) since Wed 2020-09-23 11:28:54 MDT; 2h 0min ago Process: 25483 ExecStart=/opt/runc-demo/democtl run (code=exited, status=0/SUCCESS) Main PID: 25483 (code=exited, status=0/SUCCESS)

Sep 23 11:28:54 uplifting-chihuahua systemd[1]: Starting runc demo... Sep 23 11:28:54 uplifting-chihuahua systemd[1]: Finished runc demo.

"""

In addition you should also notice an OCI container is running on the host as well: