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 permissio

Answer 1

Specific to Ubuntu, there is a known issue with lightdm that removes secondary groups from the user as part of the GUI login. You can follow that issue here: https://bugs.launchpad.net/lightdm/+bug/1781418

You can try switching off of lightdm or apply the workaround mentioned in the bug report:

[Comment out the below lines from /etc/pam.d/lightdm:]

auth optional pam_kwallet.so
auth optional pam_kwallet5.so

Temporary options include logging into your machine with something like an ssh or su -l command, or running the newgrp docker command. These will only affect the current shell and would need to be done again with each new terminal.

---

Outside of this issue, the general commands to give a user direct access to the docker socket (and therefore root access to the host) are:

sudo usermod -aG docker $(id -un) # you can often use $USER in place of the id command
newgrp docker # affects the current shell, logging out should affect all shells