Docker Notes - fcrimins/fcrimins.github.io GitHub Wiki

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See also: Web Hosting

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• Bottom line: use --volume-from into a data-only container that does nothing other than expose a volume

• The dockerfile is generated by SBT at compile. There is an SBT plugin set up in the project, that enables the sbt docker:publish and sbt docker:publishLocal commands. These compile and construct Docker image in one go.
• The name of the sbt plugin is DockerPlugin and it’s a part of the sbt native packager. The configuration for it is all in build.sbt. You compile, construct your image with sbt docker:publishLocal, which stores the image in the docker repo on your local machine. If you have the latest image locally, then docker-compose will not pull from dockerhub, but rather use local repo image.
• Is there a way to see which image is currently running?
  • A: docker-compose ps should show the containers for the project and their status.
  • the last thing to look for is whether docker-compose recreates the hamstoo container from freshly compiled image — it should state "Recreating hamstoo_hamstoo_1" instead of "Starting hamstoo_hamstoo_1" on the first lines of program output for command docker-compose up (after a fresh sbt docker:publishLocal)
• Seems like generated.keystore is being generated in /opt/docker/conf, but that's in the container right? Not on my actual filesystem?
  • Yes, it’s in the container, but also that is a linked volume, that syncs to [~/code/hamstoo/]conf/ on your local machine.
  • what are the user rights set on your [~/code/hamstoo/]conf folder? 775
    • try 777 so that docker could write the generated.keystore
• you can use docker-compose exec hamstoo bash to look inside. hamstoo is the name of the service you want to exec a command inside and bash obviously is that you want to run terminal inside the container
  • the same way you can run mongo shell docker-compose exec mongo mongo
• Error message: "236c6a10-c0d0-4522-ade8-7eb49b3ceda2/mongo STOPPED Reason: CannotCreateContainerError: API error (500): create ./mongo/configdb: "./mongo/configdb" includes invalid characters for a local volume name, only "[a-zA-Z0-9][a-zA-Z0-9_.-]" are allowed ecscompose-hamstoo:2"
  • This occurs because the host-dir, "./mongo/configdb", isn't an absolute path (doesn't start w/ a '/'), in which case it is assumed to be a volume name. See here for a suggested improvement to this error message.
  • "For example, you can specify either /foo or foo for a host-dir value. If you supply the /foo value, the Docker Engine creates a bind-mount. If you supply the foo specification, the Docker Engine creates a named volume."
  • This shows how to create a docker volume: $ docker volume create --name=foo
  • This explains how to create absolute paths.
• Error message: "STOPPED ExitCode: 255 <ip_addr>:9090->8080/tcp ecscompose-<image>:9"
  • According to this it seems like 255 is caused by non-existent directories.

• A picture is worth a thousand words.
  • "A running container is simply a standard OS process, plus file system dependencies and network connections."
• "It prevents the 'it works for me' excuses for when things break."
• "a Docker Compose script to mimic the docker run command, so we do not have to keep remembering the parameters."

• Includes a nice, seemingly comprehensive list of useful commands.
• To remove a docker image (per here):
  • $ docker rmi <sha12>

• "You can tag an image, and store multiple versions of that image with different GUIDs in a single named repository, access different tagged versions of an image with a special syntax like username/image_name:tag". For example: crimzie/hamstoo:latest
  • Amazon EC2 Container Service says this: "Namespaces are optional, and they can be included in the repository name with a slash (for example, namespace/repo"
  • The Docker Terminology link above seems to confirm this interpretation: "So, this the confusing part: Suppose there's a Docker image called thoward/scooby_snacks. The official "repository name" is thoward/scooby_snacks, even though we would normally think of the repository as just being scooby_snacks (eg, in GitHub, or elsewhere). In fact, when the Docker documentation refers to a repository, it sometimes means the whole thing, username included, and sometimes only means the part after the username."
  • Check out what's in /var/lib/docker/repositories JSON file which holds a mapping of repository names and tags, to the underlying image GUIDs in /var/lib/docker/graph/.

• $ sudo docker-compose up
• Error: Unsupported config option for services service: 'web'
  • StackOverflow says I need to be using 1.6 (or later) version of docker-compose. I was running version 1.3 that I got from apt-get.
  • For a list of versions, see the Compose file format compatibility matrix
• Error: Couldn't connect to Docker daemon at http+docker://localunixsocker - is it running?
  • Had to add sudo per here

• You can see the docker compose setup in docker-compose.yml in root folder. When used, it pulls two latest docker images from a repository (hamstoo backend and mongo db), runs them in a docker virtual machine and sets up their environment automatically.

• Don't use sudo apt-get install docker docker-compose docker-engine to install Docker. Instead follow the steps below.
  1. Remove all existing Docker packages using the following commands: apt list --installed | grep docker and sudo apt-get remove <docker_package>
  2. Follow the 'Install using the repository' instructions here.
     • "Before you install Docker for the first time on a new host machine, you need to set up the Docker repository."
  3. Continue on the same page through the 'Install Docker' section instructions, which will install docker-engine (version 1.12.6 at time of writing, 2/1/17)
  4. Per step #3-4 on this page, go to here and run the following commands:
     • $ sudo -i
     • # curl -L https://github.com/docker/compose/releases/download/1.10.0/docker-compose-`uname -s`-`uname -m` > /usr/local/bin/docker-compose
     • chmod +x /usr/local/bin/docker-compose
  5. But then I was getting an error when running docker-compose from the PATH (when running with the full absolute path, /usr/local/bin/docker-compose--note the additional 'local'--it worked fine)
     • Here's the error: bash: /usr/bin/docker-compose: No such file or directory
     • Here was the fix: sudo ln -s /usr/local/bin/docker-compose /usr/bin/docker-compose
     • Here was someone with a similar issue, which I commented on.
  6. And then I wasn't able to run docker info--but only as myself--as root it worked fine.
     • So I had to follow these steps (also referenced here), which I guess aren't so "optional."