![]() Such instructions add files, some change the user or some other setting of the image, but most often, instructions actually run some command or full script. Fully minimize and tidy up image layersĪ container image is defined by executing one image instruction after the other. ![]() dockerignore file, and we are already adding them in one COPY instruction to the image. Our CI container image is already optimized to the fullest: we have a very strict policy of only adding necessary files to our. dockerignore file we are using at Symflower starts with the following lines. dockerignore file exactly defines which files are used as the build context. However, this does not help with your build context and it becomes tedious to maintain all these instructions. However, there is also a common pitfall: when you add files to your image using the ADD or COPY instructions, you might add more than you actually need if you are adding directories.Īdding files one by one seems like the easiest way at first to make sure that you only add what you need. Such a big build context is usually a problem when you want to build your Docker images fast, as Docker needs to gather the context before actually building any layer of the image. Hence, if you have a monorepo like us, your build context is HUGE. Make the image context smallerīy default, Docker adds all files as the build context when doing a docker build. Switching to another libc implementation looks worth doing at first, but since our monster image has 6.2GB there are bigger fish to fry, at least for now. We are on ubuntu:20.04 which has only one Ubuntu competitor, namely 18.04, and we enjoy newer software more than shaving off a few measly MB. Looking at our monster CI container image One of these is called distroless by Google. for Go and Java, without adding any operating system specific files. If you do not want to go that far, there are base images specific to the application runtime you are using, e.g. it does not even add a layer to your image. Which has not only 0 MB (or in words ZERO MEGABYTES) but is also a no-op (a no-operation), i.e. However, if you want to make your base image even smaller, you might need to invest some time in making it compatible with another distribution or even with another libc implementation.įor the very adventurous, one can also use scratch as a base image. More about that later when we fully minimize our image layers. Which saves a lot of space, because tracking file changes for updates, increases your image size dramatically. Surely the Ubuntu team is looking into that already.)Īnother aspect of keeping your base image up-to-date is that you do not need to update as part of your image definition. (Why the latest versions are a few MB bigger than 18.04 is left as an exercise for the reader. Here is a list of the latest images:Īs you can see, an upgrade is not only worth the time because of better software but also because of the smaller image sizes. However, the ubuntu image changed over time and it is worth upgrading. The most used base image, ubuntu, is already very optimized. Choosing a smaller base image is therefore the first and probably the easiest way of reducing the size of your images. However, this generalization comes at the cost of including more libraries and tools that your application might not need. Base images allow to very quickly apply security and bugfix updates to your whole container based software infrastructure since a good base image serves as a general common installation. Use a smaller base image or libcĮvery container image is based upon a so called base image ( see the FROM instruction) that allows you to reuse configurations, packages and other files across different images. Splitting up processes and services for breaking up imagesĪs with everything in the world of software development and infrastructure, we can rely on best practices that others have already established by most likely wading through hours of painful research.Fully minimize and tidy up image layers.
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