How to fix "dial unix /var/run/docker.sock: connect: permission denied" when group permissions seem correct?

Question

I'm suddenly having issues after an update of Ubuntu 18.04: previously I've used docker without issue on the system, but suddenly I cannot. As far as I can tell, the permissions look correct:

$ docker run hello-world docker: Got permission denied while trying to connect to the Docker daemon socket at unix:///var/run/docker.sock: Post http://%2Fvar%2Frun%2Fdocker.sock/v1.35/containers/create: dial unix /var/run/docker.sock: connect: permission denied. See 'docker run --help'. $ ls -last /var/run/docker.sock  0 srw-rw---- 1 root docker 0 Jul 14 09:10 /var/run/docker.sock $ whoami brandon $ cat /etc/group | grep docker docker:x:995:brandon nvidia-docker:x:994: 

EDIT:

Group information:

$ groups brandon $ groups brandon brandon : brandon adm cdrom sudo dip plugdev games lpadmin sambashare docker $ whoami brandon 

Update

Since the original post where I upgraded a system from 17.04 to 18.04, I've done two upgrades from 16.04 to 18.04, and neither of the later systems had the issue. So it might be something to do with the 17.04 to 18.04 upgrade process. I've yet to perform a fresh 18.04 installation.

Answer 1

sudo setfacl --modify user:<user name or ID>:rw /var/run/docker.sock 

It doesn't require a restart and is more secure than usermod or chown.

as @mirekphd pointed out, the user ID is required when the user name only exists inside the container, but not on the host.