====== Docker ======

  * **Docker image** - operating system with preconfigured application (service)
  * **Docker container** - running instance created from docker image
  * **Data volume** - persistent storage of data outside of container. Can be shared between containers.
  * **Dockerfile** - is a recipe which describes the files, environment, and commands that make up an image.
  * **docker-compose** - tool for defining and running multi-container Docker application (e.g. web app + mysql db). Compose preserves all volumes used by your services. When docker-compose up runs, if it finds any containers from previous runs, it copies the volumes from the old container to the new container.    This process ensures that any data you’ve created in volumes isn’t lost.

====== command line ======

===== run =====
Create __new__ container based on image and execute optional command inside.
<code bash>
docker run -i --rm busybox
docker run -i --rm busybox ps aux
docker run -i --rm debian:jessie-slim
docker run -i --rm nginx bash
</code>


  * **docker run** - run __new__ isolated container ...
    * **-rm** to Automatically remove the container when it exits
    * **--restart always** 
    * **--name**

<code bash>docker run --rm -ti -v `pwd`:/opt/myservice remote/path</code>
<code>
--rm                            Automatically remove the container when it exits
-i, --interactive               Keep STDIN open even if not attached
-t, --tty                       Allocate a pseudo-TTY
-v, --volume=[]                 Bind mount a volume
</code>

How to run multiple shell commands in docker at once:
<code bash>docker run image /bin/bash -c "cd /some/path && some_command"</code>


==== stopping ====
''docker stop'' sends ''SIGTERM'' to PID1 and waits 10 seconds before force kill ''SIGKILL''.
  docker stop ----time=30 foo

  docker kill ----signal=SIGWINCH apache
  docker kill ----signal=SIGQUIT nginx
  
More on handling signals [[https://www.ctl.io/developers/blog/post/gracefully-stopping-docker-containers/]]

==== restart policy ====

<code bash>
docker update --restart=always 5ba1f7f3d67e
# or usign container name
docker update --restart=always portainer
</code>

====== GUIs ======

[[https://blog.ouseful.info/2015/08/10/seven-graphical-interfaces-to-docker/]]

Usefull:
  * <del>[[https://github.com/kevana/ui-for-docker]]</del> deprecated by:
  * [[https://github.com/portainer/portainer]]
    * <code bash>docker run -d -p 9000:9000 -v /var/run/docker.sock:/var/run/docker.sock --name portainer --restart always portainer/portainer</code>
    * [[https://portainer.readthedocs.io/en/latest/configuration.html]]

Working:
  * docker-compose-ui
    * [[https://github.com/francescou/docker-compose-ui]]

Not working:
  * [[http://panamax.io/]] 
    * CoreOS required, so they provide ready Virtualbox or Vagrant recipe
    * [[https://github.com/CenturyLinkLabs/panamax-ui/wiki/Installing-Panamax]]
    * Install command: <code bash>curl http://download.panamax.io/installer/ubuntu.sh | bash</code>

  * Generates a nice graph showing the hierarchy of Docker images in your local image cache [[https://github.com/CenturyLinkLabs/docker-image-graph]]
    * Doesn't work with current docker version


Other managers
  * https://github.com/ClusterHQ/flocker


====== Backup ======
No universal backup solution. Possible scenarios:
  * docker images - use ''docker save''
  * running container:
    * pause (but what with not flushed data?)
    * commit container as image (volumes are not included!)
    * backup a image using ''save''
  * backup data volumes
    * gracefully stop container to ensure all data are flushed
    * run new container only to execute backup script on other container's volume ''--volumes-from''
  * connect remotely to service to get dump (i.e. mysql)
  * configure service to make daily backup to bind mounted host directory

===== by committing state to images =====

To make backup of running container it is need to ''commit'' its current state and save as docker image.
With option ''-p'' container will be paused before saving snapshot.
<code bash># docker commit -p portainer portainer1
sha256:c48af304eed09c0ef7f557e6f5e02f10b2637c4c02dd765c186ee29805c31272

# docker images
REPOSITORY              TAG                 IMAGE ID            CREATED              SIZE
portainer1              latest              c48af304eed0        About a minute ago   9.16 MB
</code>

Now image can be pushed to remote hub or registry. See ''man docker push''
Or dumped to file:
<code bash>docker save -o portainer1.tar portainer1</code>
To load dump file check ''man docker load''

===== run backup on existing volume =====

To get data from container outside:
<code bash>
$ sudo docker run --rm --volumes-from dbdata -v $(pwd):/backup busybox tar cvf /backup/backup.tar /dbdata
</code>

===== exporting filesystem =====

''export'' exports only container filesystem and has some limitations: it won't export the data volume (''VOLUME'' in Dockerfile or specified by ''-v'')
<code bash>
docker export $CONTAINER_ID > $CONTAINER_ID-backup.tar
docker import - slava/$CONTAINER_ID-backup < $CONTAINER_ID-backup.tar
</code>

====== Build image ======

Create build directory and ''Dockerfile''
<file | Dockerfile>
FROM debian:jessie-slim
RUN apt-get -y update && apt-get install -y fortunes
CMD /usr/games/fortune -a | cowsay
</file>

<code bash>
docker build -t mydocker .
docker run mydocker
</code>

====== ns ======


====== Issues ======
===== endpoint with name portainer already exists in network bridge =====
<code bash>
# docker start 7cda5b580e16
Error response from daemon: endpoint with name portainer already exists in network bridge
Error: failed to start containers: 7cda5b580e16
</code>

https://github.com/moby/moby/issues/23302

Typically when you see containers in docker network inspect output with a ep- prefix, that means it can be either of 2 cases -
    these are stale endpoints left over in the DB. For those cases, docker network disconnect should help.
    these are remote endpoints seen in other nodes that are part of the overlay network. The only way to clean them up are from that specific host.


Not helping:
<code bash>docker network prune</code>
<code bash>docker network disconnect -f bridge portainer</code>



Helps:
<code bash>/etc/init.d/docker restart</code>