grml-live: use zstd instead of xz for squashfs

[zeha]

No description provided.

[github-actions]

🐳 Docker image for this PR is available:

docker pull ghcr.io/grml/grml-live:pr-442

[github-actions]

💿 ISO Build Results

The following ISO build artifacts are available from this PR:

• grml-live-build-result-initial-forky-amd64.zip (600.14 MB)
• grml-live-build-result-initial-forky-amd64-GRML_GHACI_CLOUD.zip (433.48 MB)
• grml-live-build-result-initial-forky-arm64.zip (570.28 MB)
• grml-live-build-result-initial-forky-arm64-GRML_GHACI_CLOUD.zip (414.27 MB)
• grml-live-build-result-initial-trixie-amd64.zip (600.14 MB)
• grml-live-build-result-initial-trixie-amd64-GRML_GHACI_CLOUD.zip (433.47 MB)
• grml-live-build-result-initial-trixie-arm64.zip (570.27 MB)
• grml-live-build-result-initial-trixie-arm64-GRML_GHACI_CLOUD.zip (414.26 MB)
• grml-live-build-result-repack-forky-amd64.zip (599.90 MB)
• grml-live-build-result-repack-forky-amd64-GRML_GHACI_CLOUD.zip (433.25 MB)
• grml-live-build-result-repack-forky-arm64.zip (570.02 MB)
• grml-live-build-result-repack-forky-arm64-GRML_GHACI_CLOUD.zip (414.01 MB)
• grml-live-build-result-repack-trixie-amd64.zip (599.90 MB)
• grml-live-build-result-repack-trixie-amd64-GRML_GHACI_CLOUD.zip (433.24 MB)
• grml-live-build-result-repack-trixie-arm64.zip (570.03 MB)
• grml-live-build-result-repack-trixie-arm64-GRML_GHACI_CLOUD.zip (414.01 MB)

Note: Downloads are ZIP files containing the ISO images. You need to be logged into GitHub to download. Artifacts are available for 15 days.

Build Information:

• Workflow Run: 18654595086
• Commit: 549a2c0

[mika]

I like the idea! Do we know how the ISO sizes between xz + zstd look like?
Do we expect any changes WRT boot time, memory usage,...?
Are we aware of since when (in terms of Debian releases) xz support is available?

Hm, now users don't have the option of still using LZMA/XZ, while I'm not sure that we have any actual ZLIB/gzip users out there? :p
Maybe we should even deprecate the -z option, and use xz by default, but instead allow overloading the SQUASHFS_OPTIONS so one can choose a different compression method to their very own needs? 🤔

[zeha]

Maybe we should even deprecate the -z option, and use xz by default, but instead allow overloading the SQUASHFS_OPTIONS so one can choose a different compression method to their very own needs? 🤔

I'd rather pick a setting we know works and is fine.

[crpb]

some stats with ZFS enabled of course

/grml # ls /grml/build*/*/grml_isos/*.iso -hs1t
528M /grml/build/trixie-small/grml_isos/grml-trix-small_20251024.iso
933M /grml/build/trixie-full/grml_isos/grml-trix-full_20251024.iso
548M /grml/build/sid-small/grml_isos/grml-sid-small_20251024.iso
954M /grml/build/sid-full/grml_isos/grml-sid-full_20251024.iso
542M /grml/build/forky-small/grml_isos/grml-fork-small_20251024.iso
1.1G /grml/build/forky-full/grml_isos/grml-fork-full_20251024.iso

589M /grml/build.zstd/trixie-small/grml_isos/grml-trix-small_20251024.iso
1.1G /grml/build.zstd/trixie-full/grml_isos/grml-trix-full_20251024.iso
611M /grml/build.zstd/sid-small/grml_isos/grml-sid-small_20251024.iso
1.1G /grml/build.zstd/sid-full/grml_isos/grml-sid-full_20251024.iso
603M /grml/build.zstd/forky-small/grml_isos/grml-fork-small_20251024.iso
1.2G /grml/build.zstd/forky-full/grml_isos/grml-fork-full_20251024.iso

/grml # grep -E 'Starting grml-live|Successfully finished' /grml/build*/*/grml_logs/grml-live.log
/grml/build/forky-full/grml_logs/grml-live.log:Starting grml-live [***UNRELEASED***] run on Fri Oct 24 13:09:35 CEST 2025
/grml/build/forky-full/grml_logs/grml-live.log:Successfully finished execution of grml-live [Fri Oct 24 13:18:41 CEST 2025 - running 546 seconds]
/grml/build/forky-small/grml_logs/grml-live.log:Starting grml-live [***UNRELEASED***] run on Fri Oct 24 13:18:42 CEST 2025
/grml/build/forky-small/grml_logs/grml-live.log:Successfully finished execution of grml-live [Fri Oct 24 13:24:42 CEST 2025 - running 360 seconds]
/grml/build/sid-full/grml_logs/grml-live.log:Starting grml-live [***UNRELEASED***] run on Fri Oct 24 13:24:44 CEST 2025
/grml/build/sid-full/grml_logs/grml-live.log:Successfully finished execution of grml-live [Fri Oct 24 13:33:51 CEST 2025 - running 547 seconds]
/grml/build/sid-small/grml_logs/grml-live.log:Starting grml-live [***UNRELEASED***] run on Fri Oct 24 13:33:52 CEST 2025
/grml/build/sid-small/grml_logs/grml-live.log:Successfully finished execution of grml-live [Fri Oct 24 13:39:35 CEST 2025 - running 343 seconds]
/grml/build/trixie-full/grml_logs/grml-live.log:Starting grml-live [***UNRELEASED***] run on Fri Oct 24 13:39:37 CEST 2025
/grml/build/trixie-full/grml_logs/grml-live.log:Successfully finished execution of grml-live [Fri Oct 24 13:48:26 CEST 2025 - running 529 seconds]
/grml/build/trixie-small/grml_logs/grml-live.log:Starting grml-live [***UNRELEASED***] run on Fri Oct 24 13:48:27 CEST 2025
/grml/build/trixie-small/grml_logs/grml-live.log:Successfully finished execution of grml-live [Fri Oct 24 13:53:57 CEST 2025 - running 330 seconds]

/grml/build.zstd/forky-full/grml_logs/grml-live.log:Starting grml-live [***UNRELEASED***] run on Fri Oct 24 12:06:39 CEST 2025
/grml/build.zstd/forky-full/grml_logs/grml-live.log:Successfully finished execution of grml-live [Fri Oct 24 12:15:23 CEST 2025 - running 524 seconds]
/grml/build.zstd/forky-small/grml_logs/grml-live.log:Starting grml-live [***UNRELEASED***] run on Fri Oct 24 12:15:25 CEST 2025
/grml/build.zstd/forky-small/grml_logs/grml-live.log:Successfully finished execution of grml-live [Fri Oct 24 12:21:07 CEST 2025 - running 342 seconds]
/grml/build.zstd/sid-full/grml_logs/grml-live.log:Starting grml-live [***UNRELEASED***] run on Fri Oct 24 12:21:10 CEST 2025
/grml/build.zstd/sid-full/grml_logs/grml-live.log:Successfully finished execution of grml-live [Fri Oct 24 12:29:48 CEST 2025 - running 518 seconds]
/grml/build.zstd/sid-small/grml_logs/grml-live.log:Starting grml-live [***UNRELEASED***] run on Fri Oct 24 12:29:49 CEST 2025
/grml/build.zstd/sid-small/grml_logs/grml-live.log:Successfully finished execution of grml-live [Fri Oct 24 12:35:31 CEST 2025 - running 342 seconds]
/grml/build.zstd/trixie-full/grml_logs/grml-live.log:Starting grml-live [***UNRELEASED***] run on Fri Oct 24 12:35:34 CEST 2025
/grml/build.zstd/trixie-full/grml_logs/grml-live.log:Successfully finished execution of grml-live [Fri Oct 24 12:43:59 CEST 2025 - running 505 seconds]
/grml/build.zstd/trixie-small/grml_logs/grml-live.log:Starting grml-live [***UNRELEASED***] run on Fri Oct 24 12:44:00 CEST 2025
/grml/build.zstd/trixie-small/grml_logs/grml-live.log:Successfully finished execution of grml-live [Fri Oct 24 12:49:33 CEST 2025 - running 333 seconds]