If you faced an issue like “Couldn’t connect to Docker daemon at http+docker://localunixsocket — is it running?”…

If you faced an error like in the title when you run docker-compose build, the solutions below may help you.

Is Docker engine running?

Check if Docker engine is running. Docker-compose might not have been able to access to Docker engine.

$ sudo service docker status
● docker.service - Docker Application Container Engine
   Loaded: loaded (/lib/systemd/system/docker.service; enabled; vendor preset: enabled)
   Active: active (running) since Thu 2017-12-21 19:16:26 UTC; 1h 45min ago
     Docs: https://docs.docker.com
 Main PID: 20127 (dockerd)
    Tasks: 23
   Memory: 1.0G
      CPU: 53.520s

Is the unix socket file of Docker has proper ownership?

Check if the docker Unix socket has correct file ownership. The Unix socket file should be like the following:

$ sudo ls -la /var/run/docker.sock
srw-rw---- 1 root docker 0 Dec 21 19:16 /var/run/docker.sock

Is your user in Docker user group ?

You should ensure that your user can access to Docker engine with the current privileges without sudo. It would be a good…