Gitlab: can't set domainname thru /proc/sys/kernel/domainname

[snajpa]

Yet another bug stemming from absolutely incompetent developers of Docker:

https://github.com/docker/for-linux/issues/743

[CT 17749] root@testram:~# docker-compose up
WARNING: The GITLAB_HOME variable is not set. Defaulting to a blank string.
Removing root_web_1
Recreating 7b7221faa6a7_root_web_1 ... error

ERROR: for 7b7221faa6a7_root_web_1  Cannot start service web: b'OCI runtime create failed: container_linux.go:349: starting container process caused "process_linux.go:449: container init caused \\"write sysctl key kernel.domainname: open /proc/sys/kernel/domainname: permission denied\\"": unknown'

ERROR: for web  Cannot start service web: b'OCI runtime create failed: container_linux.go:349: starting container process caused "process_linux.go:449: container init caused \\"write sysctl key kernel.domainname: open /proc/sys/kernel/domainname: permission denied\\"": unknown'
ERROR: Encountered errors while bringing up the project.

[CT 17749] root@testram:~# cat docker-compose.yml 
web:
  image: 'gitlab/gitlab-ee:latest'
  restart: always
  hostname: 'gitlab.example.com'
  environment:
    GITLAB_OMNIBUS_CONFIG: |
      external_url 'https://gitlab.example.com'
      # Add any other gitlab.rb configuration here, each on its own line
  ports:
    - '80:80'
    - '443:443'
    - '2222:22'
  volumes:
    - '$GITLAB_HOME/config:/etc/gitlab'
    - '$GITLAB_HOME/logs:/var/log/gitlab'
    - '$GITLAB_HOME/data:/var/opt/gitlab'