Permission denied when running Docker after installing it as a Snap

This is from the GitHub page, did you try these exact steps:

If you are using Ubuntu Core 16,

Connect the docker:home plug as it's not auto-connected by default:

$ sudo snap connect docker:home

If you are using an alternative snap-compatible Linux distribution ("classic" in snap lingo), and would like to run docker as a normal user:

Create and join the docker group.

$ sudo addgroup --system docker
$ sudo adduser $USER docker
$ newgrp docker

You will also need to disable and re-enable the docker snap if you added the group while it was running.

$ sudo snap disable docker
$ sudo snap enable docker

From Docker snap github

The error message tells you that your current user can’t access the docker engine, because you’re lacking permissions to access the unix socket to communicate with the engine.

Temporary solution

Use the sudo command to execute the commands with elevated permissions every time.

Permanent (suggested) solution

Add the current user to the docker group. This can be achieved by typing

sudo usermod -a -G docker $USER

You have to log out and log in again for the group membership to take effect.

Source: techoverflow.net

I assume, your username is already in docker group. To check this, issue below command.

id -nG

If not you need to add your user into the docker group by below command.

sudo groupadd docker
sudo usermod -aG docker $USER

When you execute the command, sudo systemctl start docker, it creates a docker process. That docker process contains dockerd daemon thread. The command also creates default docker.sock Unix socket. The docker.sock socket is continuously listened by dockerd daemon thread. This makes you can do kernel-level IPC with docker.pid process. To be able to use this docker socket, you need to have proper permission from the process level (docker.pid) and file level (docker.sock). So, executing below two commands should solve your issue. sudo chmod a+rwx /var/run/docker.sock # You can provide just execute permission sudo chmod a+rwx /var/run/docker.pid

sudo setfacl -m user:your_user_name:rw /var/run/docker.sock

doesn't require a restart and is more secure

You should add the user to the Docker group (see the official docs).

You can add sudo in front of the command or you can add the user in the docker group by using this command:

sudo usermod -aG docker <USER>

Log out and log back in so that your group membership is re-evaluated.