Reverse engineer a Docker run command from an existing container

During my usual backup routine, I wanted to gather how a Docker container I started a while ago was run, especially the docker run command; this is required in case I need to re-run that container and I want to preserve the options (e.g. env variables, ports, etc.).

Let’s make an example. I run a mysql docker container with:

docker run -m 100M --name testbed-mysql --restart=always -e MYSQL_ROOT_PASSWORD=foo -e MYSQL_DATABASE=bar -e MYSQLPASSWORD=foo -e MYSQL_USER=foo -v /tmp/etc:/etc/mysql/conf.d -v /tmp/mysql:/var/lib/mysql -p -d mysql

If I just list running containers, there is no way to display these options:

% docker ps -a 
CONTAINER ID        IMAGE                     COMMAND                  CREATED             STATUS              PORTS                       NAMES
a32bdcbb36c7        mysql:latest              "docker-entrypoint..."   2 days ago          Up 2 days >3306/tcp    testbed-mysql

Display this options is possible with docker inspect and some sorcery. Luckily, that sorcery is already packaged for you in two projects (alternatives):

Both of them work really well in reverse engineering the options from the running containers, as you can see:

% runlike testbed-mysql
docker run --name=testbed-mysql --hostname=a73900fe9af6 --env="MYSQL_ROOT_PASSWORD=foo" --env="MYSQL_DATABASE=bar" --env="MYSQLPASSWORD=foo" --env="MYSQL_USER=foo" --env="PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin" --env="GOSU_VERSION=1.7" --env="MYSQL_MAJOR=5.7" --env="MYSQL_VERSION=5.7.20-1" --volume="/tmp/etc:/etc/mysql/conf.d" --volume="/tmp/mysql:/var/lib/mysql" --volume="/var/lib/mysql" -p --restart=always --detach=true mysql:latest mysqld

The only option which has not been recovered is the resource constraint options I used (see -m 100M above).

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