How do I set hostname in docker-compose?

Question

In my docker-compose.yml file, I have the following. However the container does not pick up the hostname value. Any ideas?

dns:
  image: phensley/docker-dns
  hostname: affy
  domainname: affy.com
  volumes:
    - /var/run/docker.sock:/docker.sock

When I check the hostname in the container it does not pick up affy.

Answer 1

I found that the hostname was not visible to other containers when using docker run. This turns out to be a known issue (perhaps more a known feature), with part of the discussion being:

We should probably add a warning to the docs about using hostname. I think it is rarely useful.

The correct way of assigning a hostname - in terms of container networking - is to define an alias like so:

services:
  some-service:
    networks:
      some-network:
        aliases:
          - alias1
          - alias2

Unfortunately this still doesn't work with docker run. The workaround is to assign the container a name:

docker-compose run --name alias1 some-service

And alias1 can then be pinged from the other containers.

UPDATE: As @grilix points out, you should use docker-compose run --use-aliases to make the defined aliases available.