1. permission denied while trying to connect to the Docker daemon socket at unix:///var/run/docker.sock

    2. provenance
    The user that is running the docker commands (if he is a non-root user) must be added in the docker group. This is done with the following incantation: 

    sudo usermode -aG docker $USER
    … but only takes effect after a system reboot. In the meantime you can use newgrp docker in the shell you're working (this will result in a new shell with the current user being part of the docker group).

  2. [Errno 101] Network is unreachable

    3. In November 2024 when going through this docker beginners tutorial (also saved here) I encountered this trace:

    In the end I had to change the docker build invocation from: 

    docker build . -t mperdikeas/catnip
    to: 
    docker build . --network host -t mperdikeas/catnip

    In initially commented on an already existing bug report and then reported my solution here.

    The solution was found in this thread which also reports at least one additional approach.

    See also this ChatGPT thread of mine.