Docker Way
##########

Tagging Images
==============

* Image tags are not discrete copies of a file.
* The same image can have multiple tags on on your system.

.. code-block::
  :caption: Tagging docker images

  $ docker tag baku:latest gnomon/baku:1.0
  $ docker tag baku:latest gnomon/baku:latest
  $ docker images | grep cee3ab3df0c0
  gnomon/baku-docker 1.0     cee3ab3df0c0   8 weeks ago    259MB
  gnomon/baku-docker latest  cee3ab3df0c0   8 weeks ago    259MB
  baku               latest  cee3ab3df0c0   8 weeks ago    259MB
..

* Note how all three tags...

  * `baku:latest` for local use as "latest"
  * `gnomon/baku-docker:1.0` for pushing to Docker hub as "1.0"
  * `gnomon/baku-docker:latest` for pushing to Docker hub as "latest"

* ...all have the same image-id, `cee3ab3df0c0`.
* Pushing to Docker Hub is easy with...

.. code-block:: bash

  docker push gnomon/baku-docker:1.0
  docker push gnomon/baku-docker:latest
..

Specifying alternate registries
-------------------------------

* Docker hub is not the only possible registry.
* Self-hosted registries, such as Nexus [#]_ and AWS ECR [#]_ are common.
* Using the example of an AWS ECR registry in account **111222333**, we can push our Baku container there.

.. code-block:: plain
  :caption: Push image to ECR

  docker tag baku:latest \
    111222333.dkr.ecr.us-east-1.amazonaws.com/baku:1.0
  docker push 111222333.dkr.ecr.us-east-1.amazonaws.com/baku:1.0
..

.. [#] https://www.sonatype.com/products/sonatype-nexus-oss-download

.. [#] https://aws.amazon.com/ecr/

Start Scripts
=============

Systemd unit files
------------------

Docker run
^^^^^^^^^^

* Assuming...

  * a containerized application called **myapp**
  * a service user called **svc.myapp**
  * myapp files in */data/docker/myapp*
  * a port map of local 80 to the container's 8080
  * a drive map of */data/docker/myapp* to */data* in the container

.. code-block:: bash
  :caption: Unit file for a docker run example
  :linenos:

  [Unit]
  Documentation=https://docs.docker.com
  After=docker.service
  Requires=docker.service

  [Service]
  User=svc.myapp
  Group=docker
  RemainAfterExit=true
  StandardOutput=journal
  WorkingDirectory=/data/docker/myapp
  ExecStart=/usr/bin/docker run --rm --name=myapp -p80:8080 -v /data/docker/myapp:/data
  ExecStop=/usr/bin/docker stop myapp

  [Install]
  WantedBy=multi-user.target
..

Docker compose plugin
^^^^^^^^^^^^^^^^^^^^^

* The legacy `docker-compose` binary is deprecated.
* Docker now has a plugin executed with `docker compose` [#]_.

* Assuming...

  * a containerized application called **myapp**
  * a service user called **svc.myapp**
  * myapp files in */data/docker/myapp*
  * Docker Compose YAML in */data/docker/myapp/docker-compose.yml*

.. code-block:: bash
  :caption: Unit file for a docker compose example
  :linenos:

  [Unit]
  Description=Container for myapp
  Documentation=https://docs.docker.com
  After=docker.service
  Requires=docker.service

  [Service]
  Type=oneshot
  User=svc.myapp
  Group=docker
  RemainAfterExit=true
  StandardOutput=journal
  WorkingDirectory=/data/docker/myapp
  #Replace the "docker compose" with "docker-compose" for legacy builds
  #ExecStart=/bin/docker-compose up -d --remove-orphans
  #ExecStop=/bin/docker-compose down
  ExecStart=/bin/docker compose up -d --remove-orphans
  ExecStop=/bin/docker compose down

  [Install]
  WantedBy=multi-user.target
..

.. [#] https://docs.docker.com/compose/install/linux/