Docker tips¶

Running containers¶

If you know that you do not need the docker container once its stopped, you can use the --rm flag when executing docker run .... This will automatically remove the container from the host once it has stopped.

It's probably good practice to get into the habit of using this, since it forces a user to make sure any important info and data is stored in a volume.

The biggest drawback here is that you will not be able to read the container log once the container stops, since it will have been removed.

Image and Container Naming¶

It is very important to keep things organised on a shared server resource, especially with Docker. That is because it is not simple to tell who ran or built what with Docker. Most processes related to docker look like the root user ran them.

Therefore, all images and containers should be named something that includes the users US username. You should note the following implications when not naming your images and/or containers.

• All images and containers not named may be removed in order to free up space if needs be, before properly named images and containers are considered.
• If a docker container is using up an unreasonable¹ percentage of resources, and it has not been named in an intuitive way, the system admin will not know who to contact in order to follow up. As such, you will not only incur the ire of said system admin, but your container may be stopped before the work that was planned is finished.

Image Naming¶

If an image has been pulled from a remote registry, it will already have a name. This is OK, since you can just pull that image again if it's removed.

However, if the image was built locally (from a Dockerfile for example) the image name will need to be set at build time.

This can be done on the command line⁴:

docker build --tag <name[:tag]> <context>

For example:

docker build --tag ajcollett:v2.1 .

Container Naming¶

There are a few ways to name containers, however we will only cover the simplest here.

In order to add a name to a container when you run it use the following docker run option⁶:

docker run --name <your username + extra helpful things> <image name>

For example:

docker run --name ajcollett_pythonapp_v1 -it python:latest

Cleaning up¶

It is helpful for users to cleanup old containers and images they may have created, if they have not used --rm when running containers. However, this can be tricky on a shared system, especially if you haven't named your objects properly.

W.I.P