Merge branch 'trizzi-master-patch-22151' into 'master'

Add docs for reducing data transfer costs

See merge request gitlab-org/gitlab!78614

doc/user/packages/container_registry/reduce_container_registry_data_transfer.md

+---
+stage: Package
+group: Package
+info: To determine the technical writer assigned to the Stage/Group associated with this page, see https://about.gitlab.com/handbook/engineering/ux/technical-writing/#assignments
+---
+
+# Reduce Container Registry data transfers **(FREE)**
+
+Depending on the frequency with which images or tags are downloaded from the Container Registry,
+data transfers can exceed the GitLab limit. This page offers several recommendations and tips for
+reducing the amount of data you transfer with the Container Registry.
+are downloaded from the Container Registry, data transfers can exceed the GitLab limit. This page
+offers several recommendations and tips for reducing the amount of data you transfer with the
+Container Registry.
+
+## Check data transfer use
+
+Transfer usage is not available within the GitLab UI. [GitLab-#350905](https://gitlab.com/gitlab-org/gitlab/-/issues/350905)
+is the epic tracking the work to surface this information. In the interim, GitLab team members may reach out to customers that have
+significantly exceeded their transfer limits to better understand their use case and offer ways to reduce data transfer
+usage.
+
+## Determine image size
+
+Use these tools and techniques to determine your image's size:
+
+- [Skopeo](https://github.com/containers/skopeo):
+  use Skopeo's `inspect` command to examine layer count and sizes through API calls. You can
+  therefore inspect this data prior to running `docker pull IMAGE`.
+
+- Docker in CI: examine and record the image size when using GitLab CI prior to pushing an image
+  with Docker. For example:
+
+  ```yaml
+  docker inspect "$CI_REGISTRY_IMAGE:$IMAGE_TAG" \
+        | awk '/"Size": ([0-9]+)[,]?/{ printf "Final Image Size: %d\n", $2 }'
+  ```
+
+- [Dive](https://github.com/wagoodman/dive)
+  is a tool for exploring a Docker image, layer contents, and discovering ways to reduce its size.
+
+## Reduce image size
+
+### Use a smaller base image
+
+Consider using a smaller base image, such as [Alpine Linux](https://alpinelinux.org/).
+An Alpine image is around 5MB, which is several times smaller than popular base images such as
+[Debian](https://hub.docker.com/_/debian).
+If your application is distributed as a self-contained static binary, such as for Go applications,
+you can also consider using Docker's [scratch](https://hub.docker.com/_/scratch/)
+base image.
+
+If you need to use a specific base image OS, look for `-slim` or `-minimal` variants, as this helps
+to reduce the image size.
+
+Also be mindful about the operating system packages you install on top of your base image. These can
+add up to hundreds of megabytes. Try keeping the number of installed packages to the bare minimum.
+
+[Multi-stage builds](#use-multi-stage-builds) can be a powerful ally in cleaning up transient build
+dependencies.
+
+You may also consider using tools such as these:
+
+- [DockerSlim](https://github.com/docker-slim/docker-slim)
+  provides a set of commands to reduce the size of your container images.
+- [Distroless](https://github.com/GoogleContainerTools/distroless) images contain only your
+  application and its runtime dependencies. They don't contain package managers, shells, or any
+  other programs you would expect to find in a standard Linux distribution.
+
+### Minimize layers
+
+Every instruction in your Dockerfile leads to a new layer, which records the file system changes
+applied during such an instruction. In general, more or larger layers lead to larger images. Try to
+minimize the number of layers to install the packages in the Dockerfile. Otherwise, this may cause
+each step in the build process to increase the image size.
+
+There are multiple strategies to reduce the number and size of layers. For example, instead of using
+a `RUN` command per operating system package that you want to install (which would lead to a layer
+per package), you can install all the packages on a single `RUN` command to reduce the number of
+steps in the build process and reduce the size of the image.
+
+Another useful strategy is to ensure that you remove all transient build dependencies and disable or
+empty the operating system package manager cache before and after installing a package.
+
+When building your images, make sure you only copy the relevant files. For Docker, using a
+[`.dockerignore`](https://docs.docker.com/engine/reference/builder/#dockerignore-file)
+helps ensure that the build process ignores irrelevant files.
+
+You can use other third-party tools to minify your images, such as [DockerSlim](https://github.com/docker-slim/docker-slim).
+Be aware that if used improperly, such tools may remove dependencies that your application needs to
+operate under certain conditions. Therefore, it's preferable to strive for smaller images during the
+build process instead of trying to minify images afterward.
+
+### Use multi-stage builds
+
+With [multi-stage builds](https://docs.docker.com/develop/develop-images/multistage-build/),
+you use multiple `FROM` statements in your Dockerfile. Each `FROM` instruction can use a different
+base, and each begins a new build stage. You can selectively copy artifacts from one stage to
+another, leaving behind everything you don't want in the final image. This is especially useful when
+you need to install build dependencies, but you don't need them to be present in your final image.
+
+## Move to GitLab Ultimate
+
+GitLab data transfer limits are set at the tier level. If you need a higher limit, consider
+upgrading to GitLab Ultimate.
+
+## Purchase additional data transfer
+
+Read more about managing your [data transfer limits](../../../subscriptions/gitlab_com/#purchase-more-storage-and-transfer).
+
+## Related issues
+
+- You may want to rebuild your image when the base Docker image is updated. However, the
+  [pipeline subscription limit is too low](https://gitlab.com/gitlab-org/gitlab/-/issues/225278)
+  to leverage this feature. As a workaround, you can rebuild daily or multiple times per day.
+  [GitLab-#225278](https://gitlab.com/gitlab-org/gitlab/-/issues/225278)
+  proposes raising the limit to help with this workflow.