Docker command can't connect to Docker daemon

Question

I want to make a move to Docker, so I\'ve just started to mess around with it. I\'ve installed Docker on a VirtualBox Ubuntu 15.10 (Wily Werewolf) installation and as sugges

Answer 1

For Ubuntu:
Happened with me when I updated docker.
You need to unmask the service and socket and then restart the service.

Following worked for me:

systemctl unmask docker.service
systemctl unmask docker.socket
systemctl start docker.service

What happend behind the scenes
systemd also has the ability to mark a unit as completely unstartable, automatically or manually, by linking it to /dev/null. This is called masking the unit, and is possible with the mask command.

sudo systemctl mask docker.service

You can check the list of masked services using:

sudo systemctl list-unit-files

To enable auto/manual start of service you need to unmask it using:

sudo sytemctl unmask docker.service

Now the service will be enabled as shown below