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Pull request overview
This PR reduces Flatcar customData size by embedding generated file payloads into a single tarball that’s included in Ignition customData and extracted during early boot (since Ignition customData itself can’t be gzipped).
Changes:
- Pack Flatcar
write_files+bootcmdartifacts into a tarball, embed it in Ignition, and extract it at boot via a new systemd unit. - Remove the previous “Ignition envelope” wrapping approach for Flatcar customData generation.
- Update Flatcar snapshot testdata and unit tests to validate the tarball-based approach.
Reviewed changes
Copilot reviewed 4 out of 10 changed files in this pull request and generated 3 comments.
Show a summary per file
| File | Description |
|---|---|
| pkg/agent/baker.go | Builds a tarball from cloud-init payloads, embeds it in Ignition, and stops using the prior envelope wrapping for Flatcar. |
| parts/linux/cloud-init/flatcar.yml | Adds ignition-file-extract.service to extract the tar payload before ignition-bootcmds.service runs. |
| pkg/agent/utils.go | Adds a gzip decode helper used by the new tarball pipeline and tests. |
| pkg/agent/baker_test.go | Updates tests/helpers to decode and inspect the tarball payload, and adjusts Flatcar expectations (units/files). |
| pkg/agent/testdata/Flatcar/CustomData | Refreshes Flatcar customData snapshot to match the new tarball + extract-unit format. |
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pkg/agent/baker.go
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nit: can we set this up top as the default and then avoid the nested if/else?
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sure, reworked the nesting into a flat block
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The tarball is extracted very early during boot. Doing it this way makes compression equally effective as cloud-init's whole config compression and gets rid of the size problems we were hitting with the previous approach for flatcar. The previous approach was effectively: base64(gzip([]base64(gzip(files)))) while the new one is more like base64(gzip([]files)). Cloud-init does: gzip([]base64(gzip)).
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awesomenix
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cameronmeissner
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|
Testing Flatcar changes here https://msazure.visualstudio.com/CloudNativeCompute/_build/results?buildId=151725830&view=results |
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Cherry-pick 068403d with conflict resolution: - flatcar.yml: kept Issue 9 symlink workaround AND new ignition-file-extract.service - Added storage.links symlink for ignition-file-extract.service (Issue 9 compat) - Testdata regenerated via make generate CustomData reduced from 62,761 to 55,991 chars (~11% smaller).
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Cherry-pick 068403d with conflict resolution: - flatcar.yml: kept Issue 9 symlink workaround AND new ignition-file-extract.service - Added storage.links symlink for ignition-file-extract.service (Issue 9 compat) - Testdata regenerated via make generate CustomData reduced from 62,761 to 55,991 chars (~11% smaller).
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What this PR does / why we need it:
This PR changes the way customdata is handled for Flatcar nodepools, by packing up all file contents into a tarball, putting that into the customdata and unpacking at runtime. This allows the file contents to be compressed more efficiently than before. Flatcar's customdata handler (ignition) does not support gzipped customdata.
Which issue(s) this PR fixes:
Fixes #