Docker: Are you trying to connect to a TLS-enabled daemon without TLS?

Question

On Linux Mint 17.1 x86_64 with kernel 3.13.0-48-generic and OpenSSL version 1.0.1f-1ubuntu2.11; whenever I try to execute any docker command (like docker login or <

Answer 1

This can happen when the docker service is unable to start. sudo service docker start or restart returning no output does not mean that it started successfully. You can use sudo /etc/init.d/docker status to find out if, and why, it failed to start.

In my case, it was due to lack of disk space.

username@computer:~$ sudo service docker restart
username@computer:~$ sudo /etc/init.d/docker status
? docker.service - Docker Application Container Engine
   Loaded: loaded (/lib/systemd/system/docker.service; enabled; vendor preset: enabled)
   Active: failed (Result: start-limit) since Mon 2015-12-21 15:11:59 PST; 21s ago
     Docs: http://docs.docker.com
  Process: 26463 ExecStart=/usr/bin/docker -d -H fd:// $DOCKER_OPTS (code=exited, status=1/FAILURE)
 Main PID: 26463 (code=exited, status=1/FAILURE)

Dec 21 15:11:59 computer docker[26463]: time="2015-12-21T15:11:59-08:00" level=info msg="Listening for HTTP on fd ()"
Dec 21 15:11:59 computer docker[26463]: time="2015-12-21T15:11:59-08:00" level=info msg="+job init_networkdriver()"
Dec 21 15:11:59 computer docker[26463]: time="2015-12-21T15:11:59-08:00" level=info msg="-job init_networkdriver() = OK (0)"
Dec 21 15:11:59 computer docker[26463]: time="2015-12-21T15:11:59-08:00" level=fatal msg="Shutting down daemon due to errors: Insertion failed because database is full: database or disk is full"
Dec 21 15:11:59 computer systemd[1]: docker.service: main process exited, code=exited, status=1/FAILURE
Dec 21 15:11:59 computer systemd[1]: Unit docker.service entered failed state.
Dec 21 15:11:59 computer systemd[1]: docker.service failed.
Dec 21 15:11:59 computer systemd[1]: start request repeated too quickly for docker.service
Dec 21 15:11:59 computer systemd[1]: Failed to start Docker Application Container Engine.
Dec 21 15:11:59 computer systemd[1]: docker.service failed.

After deleting some files, I was able to restart the service and run docker containers normally.