I'm trying to installed Docker on a Vagrantbox with Ubuntu 14.04 using the instructions on the official website (Docker Docs). The installation seemed to work, but afterwards I can't start the docker service using sudo service docker start it gives me the following error message:

start: Job failed to start

If I try docker ps -a then I get the following error message:

Cannot connect to the Docker daemon. Is the docker daemon running on this host?

Kernel: Linux vagrant-ubuntu-trusty-64 3.13.0-85-generic #129-Ubuntu SMP Thu Mar 17 20:50:15 UTC 2016 x86_64 x86_64 x86_64 GNU/Linux

Relevant lines from /var/log/upstart/docker.log

Waiting for /var/run/docker.sock Invalid value "" for flag --mtu: strconv.ParseInt: parsing "": invalid syntax

  • 3
    Check the actual logs for docker, likely at /var/log/upstart/docker.log. Update your question if there are other relevant lines
    – brent
    Apr 25 '16 at 17:59

As mentioned by @brent the solution was looking into the logs at /var/log/upstart/docker.log, which showed that the --mtu parameter was empty. In my case it was dependent on a environment variable that wasn't set.

  • 1
    Great, glad you sorted it
    – brent
    Apr 26 '16 at 16:47
  • and where did you fix the missing parameter?
    – wranvaud
    Jul 14 '17 at 20:31

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