Added post on enabling docker TCP socket with Systemd socket activation.

Bind dockerd to a TCP port

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:date: 2018-01-08

:summary: Bind dockerd to a TCP port

On a modern system (one running Systemd) when installing Docker, the

:code:`dockerd` daemon is run using Systemd' socket activation. By default the

socket is :code:`/var/run/docker.sock`. If you want to connect to a remote

machine over TCP, the obvious thing to do is to create

:code:`/etc/docker/daemon.json` and set the :code:`hosts` list there. But that

will conflict with the command line flags for socket activation. The correct way

is to override Systemd' socket activation config. Here's how (all command are as

:code:`root`):

.. code:: shell

    mkdir -p /etc/systemd/system/docker.socket.d

    echo '[Socket]' > /etc/systemd/system/docker.socket.d/tcp.conf

    echo 'ListenStream=2375' >> /etc/systemd/system/docker.socket.d/tcp.conf

    systemctl daemon-reload

    systemctl restart docker