chore(images): compress disk images with xz instead of zstd#3107
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- Package release images as `.img.xz` (`xz -9e -T0`) instead of `.img.zst` - Fixes flashing in balenaEtcher, which has no native zstd support - ~12% smaller downloads than zstd -19 (794 MB vs 907 MB on pi4-64) - Update rpi-imager JSON generator + tests to match `.img.xz` assets - Update install docs/FAQ; drop the Etcher "decompress first" workaround Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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Pull request overview
Switches release disk-image compression from zstd (.img.zst) to xz (.img.xz) so that release artifacts can be flashed directly by both Raspberry Pi Imager and balenaEtcher, and updates the Raspberry Pi Imager JSON tooling + docs accordingly.
Changes:
- Update the disk-image build workflow to produce
.img.xzartifacts (and matching checksums/metadata). - Update the Raspberry Pi Imager JSON generator (and tests) to discover
.img.xzassets. - Update website “get started” + installation/FAQ docs to reference
.img.xzandxz -dextraction.
Reviewed changes
Copilot reviewed 7 out of 7 changed files in this pull request and generated 2 comments.
Show a summary per file
| File | Description |
|---|---|
| website/layouts/_default/get-started.html | Updates the website “Pre-built disk images” blurb to reference .img.xz instead of .zst. |
| website/data/faq.yaml | Updates macOS Imager FAQ guidance to reference .img.xz and xz -d. |
| website/content/docs/installation-options.md | Updates installation docs to reflect .img.xz assets and removes Etcher-specific zstd workaround. |
| tools/raspberry_pi_imager/tests/test_build_pi_imager_json.py | Adjusts unit tests to expect .img.xz release assets and non-image filtering. |
| tools/raspberry_pi_imager/README.md | Updates tool documentation to describe filtering .xz assets. |
| tools/raspberry_pi_imager/build_pi_imager_json.py | Updates asset filtering/board parsing and metadata URL derivation for .img.xz. |
| .github/workflows/build-balena-disk-image.yaml | Changes CI packaging from zstd to xz and updates artifact/attestation patterns accordingly. |
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Addresses Copilot review on #3107. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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Issues Fixed
No linked issue. Distributable disk images were compressed with zstd (
.img.zst), which balenaEtcher cannot flash — Etcher has no native zstd support (etcher#2856 is still open), forcing users to manually decompress first. Raspberry Pi Imager's zstd path has also been flaky.Description
Switch release disk-image compression from zstd to xz (
.img.xz,xz -9e -T0).xzis the only format flashed natively out of the box by both Raspberry Pi Imager and balenaEtcher, and is the format official Raspberry Pi OS images already ship as.pi4-64image (4.67 GB raw): xz is ~12% smaller than the current zstd (794 MB vs 907 MB). Kept-T0(multi-threaded) — single-threaded shaved only ~0.7% more but took ~4× longer..img.xzassets.Checklist