Docker is fantastic right up until it throws one of its greasy, context-free error messages at you and you lose twenty minutes to a thing that has a one-line fix. I've been collecting these — the exact strings, and the first thing to check for each. Here are the ten that eat the most time.
1. Cannot connect to the Docker daemon at unix:///var/run/docker.sock
The engine isn't reachable. In order of likelihood: the daemon isn't running (systemctl status docker), you're not in the docker group (sudo usermod -aG docker $USER, then log out and back in), or you're pointing at the wrong DOCKER_HOST. It's almost never Docker being broken — it's Docker not being up or you not being allowed.
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2. no space left on device
