Docker-Compose can't connect to Docker Daemon

Question

I am getting an error message saying I can\'t connect to the docker daemon. I have looked into other people\'s answers who have had similar issues but it hasn\'t helped. I

Answer 1

It appears your issue was created by an old Docker bug, where the socket file was not recreated after Docker crashed. If this is the issue, then renaming the socket file should allow it to be re-created:

$ sudo service docker stop
$ sudo mv /var/lib/docker /var/lib/docker.bak
$ sudo service docker start

Since this bug is fixed, most people getting the error Couldn't connect to Docker daemon are probably getting it because they are not in the docker group and don't have permissions to read that file. Running with sudo docker ... will fix that, but isn't a great solution.

Docker can be run as a non-root user (without sudo) that has the proper group permissions. The Linux post-install docs has the details. The short version:

$ sudo groupadd docker
$ sudo usermod -aG docker $USER
# Log out and log back in again to apply the groups
$ groups  # docker should be in the list of groups for your user
$ docker run hello-world  # Works without sudo

This allows users in the docker group to run docker and docker-compose commands without sudo. Docker itself runs a root, allowing some attacks, so you still need to be careful with what containers you run. See Docker Security Documentation for more details.