After installation or just after a an OS update or some package update docker engine starts to complain about insufficient permissions.
Particularly it complains about permission to access /var/run/docker.sock

docker ps
// permission denied message

$> ls -la /var/run/docker.sock

The output should show root:docker as {ownder}:{group}.
Run also

ls -l /lib/systemd/system/docker.socket

The output should show root:docker as {ownder}:{group}.
If it shows root:root there is a problem

sudo chgrp docker /lib/systemd/system/docker.socket

Check the following:

groups

Current user should be member of these groups: docker, kvm.
if the docker group doesn't exist add it

sudo groupadd docker

If the new group is added or the group is there but current user is not a member, add it.

sudo usermod -aG kvm $USER

The current user now should be visible in group file /etc/group
or when running

getent group

or simply

groups

If not try running:

sudo su $USER -c groups

If the list of groups contain kvm and docker you need to log out and log back in or somehow restart system-auth.
After that it should work or there is further problem unrelated to the above.

verify

docker ps