[Internal]: Add the slim Elastic Package Registry images to the air-gapped EPR docs #9247

Description

What: The Elastic Package Registry (EPR) now publishes lighter Docker distribution images with a -slim suffix. Users who host their own EPR in an air-gapped environment should be able to find these images, understand how they differ from the current ones, and use the slim image as the recommended choice.

What users need to know, compared with the existing images:

• Size. On disk, production is about 70.4 GB and production-slim about 10.3 GB (around 85% smaller). lite is about 25.6 GB and lite-slim about 3.38 GB. Transferring and loading the image is the step air-gapped users struggle with, and the current page only says "Check the image size to ensure that you have enough disk space."
• Kibana compatibility. The slim images only include package versions compatible with Kibana 8.15 to 9.5. They include no packages for Kibana 7.x. Anyone running 7.x Kibana must keep using the full images.
• Fewer versions per package. production-slim keeps 3 versions per package for each supported Kibana release, instead of every version ever published. The full images remain available for users who need an older package version.
• Pre-release builds. -preview, -rc, and -dev package builds are not included in lite-slim.

Requested changes:

1. Run Elastic Agents in an air-gapped environment → Host your own Elastic Package Registry. This page lists the available distributions. Today it has 9.5.6 (recommended), lite-9.5.6, production, and lite, with no slim images. Add the slim distributions, make the slim image the recommended one, and use it in the pull, save, load, and run steps. A short note on what slim leaves out (no 7.x packages, a limited number of versions) helps users decide when they still need the full image.
2. Air-gapped install → Elastic Package Registry. This page links to page 1 for the image list. Its "Script to generate a SystemD service file" and "SystemD service file" examples hardcode EPR_IMAGE="docker.elastic.co/package-registry/distribution:9.5.6". Switch them to the recommended slim image.

Exact wording and placement are the writer's call.

Version scoping. Both pages cover several stack versions, and slim tags exist only from the releases listed below. Releases before those (for example 9.5.0–9.5.5, or the "Specific version" tab with 9.0.0) have no -slim tag and still need the full image. The pages need a version-scoped split, not a blanket replacement of 9.5.6 with 9.5.6-slim.

Open questions:

• Lifecycle state of the slim images (GA or technical preview) has not been confirmed. Note that the distribution tool that builds them is in technical preview, which is a separate question from the images themselves.
• Should the docs also list the rolling production-slim and lite-slim tags, the counterparts of the existing production and lite entries?

When: Already published. The first releases with slim tags are 8.19.24, 9.4.9, and 9.5.6, and they will also ship with 9.6.0. Older releases will not be re-tagged.

Why: The full production image carries every version of every package ever published, with no retention policy. It is about 20 GB compressed and about 70 GB on disk, which makes it hard to pull, transfer into an air-gapped network, store, and scan. The slim images contain only the package versions Kibana can actually use.

Applies to self-managed and ECK deployments that host their own EPR, from 8.19.24, 9.4.9, 9.5.6, and 9.6.0. Not applicable to serverless.

Resources

• Internal announcement draft with sizes, package counts, and build details (Elastic-internal): https://docs.google.com/document/d/1kqUdFKNbkZZ9OsSzbOHHW9el6D8_iJVVC8VFSV7aL7w/edit?tab=t.0
• Release tagging of the slim images: feat(distribution): re-tag slim distributions on release package-registry#2150 and Remove transitional FIPS and slim image availability guards package-registry#2244
• Slim distribution definitions: production-slim.yaml and lite-slim.yaml
• Related, out of scope for this issue: [REQUEST]: Include steps to customize packages for the Elastic Package Registry container #7763 (building a custom EPR image)

Which deployment methods does this change impact?

Elastic On-Prem only (ECE, ECK, or self-managed)

What Elastic Stack release is this request related to?

9.5

Collaboration model

The documentation team will create the first draft

Point of contact.

Main contact: @teresaromero

Stakeholders: