title: docker-compose up with error "Couldn't connect to Docker"
body: <p>start learning docker / docker-compose and after some tutorials I thought I have found a good one. </p>
  
  <pre><code>https://github.com/sprintcube/docker-compose-lamp/tree/master/config/php
  </code></pre>
  
  <p>After installing and preparing I did:</p>
  
  <pre><code>sudo service docker start
  </code></pre>
  
  <p>and </p>
  
  <pre><code>docker-compose up -d
  </code></pre>
  
  <p>but it failed with this message: </p>
  
  <pre><code>dev@terra-dev:~/Projekte/docker-compose-lamp$ docker-compose up -d
  ERROR: Couldn't connect to Docker daemon at http+docker://localunixsocket - is it running?
  
  If it's at a non-standard location, specify the URL with the DOCKER_HOST environment variable.
  </code></pre>
  
  <p>Where do I have to define the docker host? In my docker-compose file? Or somewhere else?</p>
  
  <p>regards n00n</p>
  
  <p>update: Result of sudo service docker status: </p>
  
  <pre><code>docker.service - Docker Application Container Engine
     Loaded: loaded (/lib/systemd/system/docker.service; disabled; vendor preset: enabled)
     Active: active (running) since Sun 2019-10-06 13:25:25 CEST; 9s ago
       Docs: https://docs.docker.com
   Main PID: 2640 (dockerd)
      Tasks: 14
     CGroup: /system.slice/docker.service
             └─2640 /usr/bin/dockerd -H fd:// --containerd=/run/containerd/containerd.sock
  
  Okt 06 13:25:24 terra-dev dockerd[2640]: time="2019-10-06T13:25:24.087358085+02:00" level=warning msg="Your kernel does not support cgroup rt period"
  Okt 06 13:25:24 terra-dev dockerd[2640]: time="2019-10-06T13:25:24.087381826+02:00" level=warning msg="Your kernel does not support cgroup rt runtime"
  Okt 06 13:25:24 terra-dev dockerd[2640]: time="2019-10-06T13:25:24.092676335+02:00" level=info msg="Loading containers: start."
  Okt 06 13:25:24 terra-dev dockerd[2640]: time="2019-10-06T13:25:24.732654311+02:00" level=info msg="Default bridge (docker0) is assigned with an IP address 17
  Okt 06 13:25:24 terra-dev dockerd[2640]: time="2019-10-06T13:25:24.959702995+02:00" level=info msg="Loading containers: done."
  Okt 06 13:25:25 terra-dev dockerd[2640]: time="2019-10-06T13:25:25.020225493+02:00" level=warning msg="failed to retrieve runc version: unknown output format:
  Okt 06 13:25:25 terra-dev dockerd[2640]: time="2019-10-06T13:25:25.096346086+02:00" level=info msg="Docker daemon" commit=2d0083d graphdriver(s)=overlay2 vers
  Okt 06 13:25:25 terra-dev dockerd[2640]: time="2019-10-06T13:25:25.103672560+02:00" level=info msg="Daemon has completed initialization"
  Okt 06 13:25:25 terra-dev dockerd[2640]: time="2019-10-06T13:25:25.148505614+02:00" level=info msg="API listen on /var/run/docker.sock"
  Okt 06 13:25:25 terra-dev systemd[1]: Started Docker Application Container Engine.
  </code></pre>