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49 lines
2.0 KiB
49 lines
2.0 KiB
[[_TOC_]]
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# Good Docker Practices
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## Keep the Docker image simple (micro-services)
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Although you can run as many processes in a single container as you want,
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it is usually a good idea to design a container to do a single task. If
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your application does several different things you can always add
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"sidecar" containers that do the extra work.
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There will be situations where splitting an application into different
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containers is too complicated. Be flexible and use your own judgement.
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## Use small base images
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A smaller image means faster start-up times and less memory used on the
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container host. One way to acheive is to use a small base image. A popular
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small image is `alpine` based on Alpine Linux. This is a complete Linux
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with image size of 5.5MB with its own packages. By comparison,
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`debian:buster-slim` is about 70MB.
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On the other hand, don't let the drive toward small size get in the way
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of needed functionality; remember the IBM Pollyanna Principle: "machines
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should work; people should think".
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## When possible use container orchestration
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Getting containers to interact and cooperate can be tricky, so use one of
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the orcestration tools like Kubernetes or Docker Compose to do this.
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## Use CI/CD (i.e., automation) to keep Docker images up-to-date
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Set up automation to rebuild your Docker images periodically making sure
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that you disable caching when building. This way your image will have the
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most up-to-date and secure base images.
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## Send diagnostic output to standard output
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In the traditional server world we are used to sending logs to files. With
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Docker containers it is usually better to send diagnostic output to
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standard output. Kubernetes and other orchestration tools are designed
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with the expectation that logging is sent to standard output.
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## Run containers in "read-only" mode
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Running a Docker container in read-only mode helps to reduce the attack
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surface area of your application. Mount external volumes for those parts
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of the file system that need to be writable (`/var/log`, `/tmp`, etc.).
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