Rename a project by keeping containers

Question

I decided to change the project name of a docker composition:

$ docker-compose -p old_name up -d # Before
Starting old_name_web_1
$ docker-compose -p new_name up -d # After
Creating new_name_web_1

But I don't wanted to delete my containers, so I renamed them:

$ docker rename old_name_web_1 new_name_web_1
...

I thought docker-compose was based on container names, but it does not seem to be the case:

$ docker-compose -p new_name up -d

ERROR: for web Cannot create container for service web: Conflict. The name "/new_name_web_1" is already in use by container 4930deaabb[...]. You have to remove (or rename) that container to be able to reuse that name. ERROR: Encountered errors while bringing up the project.

How can I relink my old containers to the new composition ?

Answer 1

It looks like you are using one of the newer versions of docker compose which tracks containers by labels assigned to them rather than by their names. That is why renaming the container didn't work.

Updating labels

You can check container's labels through the docker inspect command.

$ docker inspect --format='{{json .Config.Labels }}' container_name

The project name is the value of the 'com.docker.compose.project' label.

Moving an existing container to a new project is as easy as changing the value of that label. However it is not yet supported by Docker CLI. There is an open issue requesting that feature.

Workaround

It still can be achieved by directly editing the configuration file of that particular container. There you will find labels currently assigned to that container.

$ nano /var/lib/docker/containers/$container_id/config.v2.json

Assign the new project name to the 'com.docker.compose.project' label and save the file. Next you have to restart the daemon. Otherwise the changes will not be visible to docker.

$ systemctl daemon-reload

Answer 2

While it is true docker-compose reuse existing containers, this comment mentions:

docker-compose by default uses the folder name of the yml file as the project name, and prefix that name to all container names.

This could explain why docker-compose up did not pick up the new container name.