docker-compose image named: “prefix_%s_1” instead of “%s”

Question

When I set up a couple of Docker containers in docker-compose.yaml file with links, the name of the containers ends up being of the format prefix_%s_1

Answer 1

You could just set container name to what you want via container_name:

redis:
    build: ../storage/redis
    container_name: redis
    ports:
      - "6379:6379"

And container hostname could also be set via hostname.

Answer 2

That's just how docker-compose names containers so that it can manage them.

The basename is the name of the directory containing the docker-compose.yaml file. This is followed by the name of the container as specified in your docker-compose.yaml file, and finally that is followed by an instance number which increases if you bring up multiple instances of a container using something like docker-compose scale.

This naming scheme is how docker-compose is able to identify your containers when you attempt to operate on them using something like docker-compose stop.

I don't think this conflicts with the documentation in any way. That is, if I start with, say, this docker-compose.yaml in a directory named sotest:

irc:
  image: docker.io/xena/elemental-ircd
  links:
    - web

web:
  image: larsks/thttpd

And then bring up the compose:

$ docker-compose up

I get two containers:

CONTAINER ID        IMAGE                           ...NAMES
960c1491c03e        docker.io/xena/elemental-ircd   ...sotest_irc_1
422bba313e71        larsks/thttpd                   ...sotest_web_1

If I look at the /etc/hosts file inside of sotest_irc_1, I see:

172.17.0.28 web 422bba313e71 sotest_web_1

In addition to a number of other names. So the linked host is available by name as described in the docs.

Answer 3

According to docker compose issue #745:

By default, Compose bases the project name on basename of the directory compose commands are run from. The project name can be overridden either by passing a -p / --project-name option for each command or setting the COMPOSE_PROJECT_NAME environment variable.

You can set the prefix of your choice to your container names by writing something like this:

$ docker-compose -p MY_PROJECT_NAME

which is the equivalent to (the more readable):

$ docker-compose --project-name MY_PROJECT_NAME

Answer 4

Docker compose will use the name of the directory with your compose file as the name of the project unless you set if via the -p option

-p, --project-name NAME     Specify an alternate project name (default: directory name)

Compose supports declaring default environment variables in an environment file named .env placed in the folder where the docker-compose command is executed (current working directory).

Where you'll want to set COMPOSE_PROJECT_NAME