Use images for more than their default program: read files, test a config and run a backup job with different arguments.

Print the Alpine release with a one-off container:

Keep the next one, so its output stays in its logs:

docker run --name osinfo alpine:3.20 cat /etc/os-release
docker logs osinfo

pier/web:1.0 does not start. Test its nginx configuration instead of starting the server:

pier/backup:1.0 has an entrypoint. Read how it is built:

docker image inspect --format 'ENTRYPOINT={{json .Config.Entrypoint}} CMD={{json .Config.Cmd}}' pier/backup:1.0

Create backup-users, which backs up users instead of all:

docker run --name backup-users pier/backup:1.0 users

Finally, read the script itself. Passing cat after the image only hands it to backup.sh; replace the entrypoint:

docker run --rm --entrypoint cat pier/backup:1.0 /usr/local/bin/backup.sh