Drop redundant staging dir symlink for sysext files

[bsherman]

Currently, updex mimics sysupdated behavior and respects the CurrentSymlink directive, thus it creates this symlink in the staging dir (/var/lib/extensions.d). However, the symlink is not used, only provided as an indicator of the current sysext version when multiple versions are downloaded. In addition, updex createx a symlink to the most recently downloaded version of a sysext in the /var/lib/extensions directory. This symlink performs the important role of enabling systemd-sysext to see and merge the sysext filesystem, but it is implicitly provides a redundant implementation of "current version" indication.

Frostyard sysexts should not include the CurrentSymlink directive, but if it is missing in the transfer file, updex will fail to download the sysext.

Needed changes follow:

1. updex should assume the name of the symlink in /var/lib/extensions will be named .raw given a transfer match patern of <name>_@v_%w_%a.raw[.compression extensions]
2. updex should not depend on CurrentSymlink (eg, symlink in staging dir) for managing the symlink in /var/lib/extensions at any point
3. updex update/enable should notice if CurrentSymlink exists in a transfer file and if the named symlink exists, updex should remove it

[bketelsen]

— Automated by Yeti —

Implementation Plan

Now I have full context. Here's the updated plan:

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Implementation Plan: Drop redundant staging dir symlink for sysext files

Summary

Make CurrentSymlink fully optional. Derive the /var/lib/extensions/ symlink name from the transfer file's Component name (derived from the .transfer filename) plus the extension from Target.MatchPattern. Stop creating staging-dir symlinks entirely, and clean up existing ones when CurrentSymlink is present.

Single PR

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1. Add SysextLinkName helper

File: sysext/manager.go — new exported function

func SysextLinkName(t *config.Transfer) string {
    return t.Component + filepath.Ext(t.Target.MatchPattern)
}

Component is already derived from the .transfer filename (e.g., foo.transfer → foo). filepath.Ext(t.Target.MatchPattern) extracts the file extension from the target pattern (e.g., .raw from foo_@v_%w_%a.raw). This yields foo.raw.

No fallback to CurrentSymlink. No pattern matching heuristics.

File: sysext/manager_test.go — add TestSysextLinkName with cases:

• Component "myext", MatchPattern "myext_@v.raw" → "myext.raw"
• Component "myext", MatchPattern "myext_@v_%w_%a.raw" → "myext.raw"
• Component "my_ext", MatchPattern "my_ext_@v.raw" → "my_ext.raw"

---

2. Rewrite LinkToSysext — accept targetFile, use derived name

File: sysext/manager.go — modify LinkToSysext (line 259)

New signature: LinkToSysext(t *config.Transfer, targetFile string) error

New behavior:

• Derive sysext symlink name via SysextLinkName(t)
• Build the full path to the versioned file: filepath.Join(t.Target.Path, targetFile)
• Create symlink at filepath.Join(SysextDir, SysextLinkName(t)) → full path to versioned file
• Remove the CurrentSymlink == "" error guard (lines 260–262)
• Remove the staging symlink resolution logic (lines 265–279) — the target file is passed directly

This eliminates the two-hop dependency (staging symlink → resolve → sysext symlink) in favor of a direct link.

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3. Rewrite UnlinkFromSysext — use derived name

File: sysext/manager.go — modify UnlinkFromSysext (line 308)

• Replace t.Target.CurrentSymlink with SysextLinkName(t) to determine the symlink path in /var/lib/extensions/
• Remove the CurrentSymlink == "" error guard (lines 309–311)

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4. Update GetInstalledVersions — read sysext dir symlink

File: sysext/manager.go — modify GetInstalledVersions (line 40)

Replace lines 60–68 (which read the staging CurrentSymlink) with:

sysextLink := filepath.Join(SysextDir, SysextLinkName(t))
if target, err := os.Readlink(sysextLink); err == nil {
    if v, _, ok := version.ExtractVersionParsed(filepath.Base(target), patterns); ok {
        current = v
    }
}

This reads the /var/lib/extensions/<name>.raw symlink to determine the current version. The existing fallback (lines 83–87, newest-is-current) remains for when no symlink exists.

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5. Update GetActiveVersion — read sysext dir symlink

File: sysext/manager.go — modify GetActiveVersion (line 94)

Replace lines 100–108 (which read the staging CurrentSymlink) with:

sysextLink := filepath.Join(SysextDir, SysextLinkName(t))
if target, err := os.Readlink(sysextLink); err == nil {
    if v, _, ok := version.ExtractVersionParsed(filepath.Base(target), patterns); ok {
        return v, nil
    }
}

Keep the /run/extensions fallback (lines 110–124) unchanged.

---

6. Update RemoveAllVersions — clean up staging symlinks

File: sysext/manager.go — modify RemoveAllVersions (line 328)

Replace lines 346–355 (which only remove if CurrentSymlink != "") with: if t.Target.CurrentSymlink != "", remove filepath.Join(targetDir, t.Target.CurrentSymlink) best-effort. This handles legacy cleanup.

The existing loop at lines 357+ already skips symlinks when counting versions. No other changes needed.

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7. Update installTransfer — remove staging symlink creation, add cleanup

File: updex/install.go — modify installTransfer

1. Remove lines 82–88 (the UpdateSymlink call for CurrentSymlink in the staging dir)
2. Update the LinkToSysext call (line 91) to pass targetFile: sysext.LinkToSysext(transfer, targetFile)
3. Add after LinkToSysext: best-effort cleanup of any existing staging CurrentSymlink:

   if transfer.Target.CurrentSymlink != "" {
       os.Remove(filepath.Join(transfer.Target.Path, transfer.Target.CurrentSymlink))
   }

   No warning, no error — just silent cleanup per issue requirement inconsistent check for root privileges #3.

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8. Update tests

File: sysext/manager_test.go

• Add TestSysextLinkName (step 1 above)
• TestGetInstalledVersionsWithSymlink (line 60): Update to place the symlink in a mock sysext dir rather than the staging dir, or adjust to test the fallback (newest-is-current) behavior since the test environment won't have /var/lib/extensions
• TestUpdateSymlink and TestUpdateSymlinkReplace: If UpdateSymlink is no longer called anywhere after removing the staging symlink creation from installTransfer, remove these tests along with the UpdateSymlink function itself
• Add TestLinkToSysextWithoutCurrentSymlink: Verify LinkToSysext works when CurrentSymlink is empty (the primary goal of this change)
• Add test: staging CurrentSymlink cleanup in installTransfer
• Update all test fixtures that set CurrentSymlink to also have cases where it is absent

File: updex/ tests — update any integration tests that set CurrentSymlink to verify they still work without it.

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9. Remove UpdateSymlink if unused

File: sysext/manager.go — after step 7, UpdateSymlink (line 130) is no longer called. Grep for remaining callers. If none, remove the function and its tests. It's exported, but this is an acceptable breaking change in a minor version bump.

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10. Update documentation

File: yeti/OVERVIEW.md — line ~129: remove "update CurrentSymlink" from the data flow description.

File: yeti/config-reference.md — update the CurrentSymlink entry to note it is deprecated and ignored for symlink creation (only used for cleanup of legacy symlinks if present).

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Files changed (summary)

File	Change
sysext/manager.go	Add SysextLinkName(), rewrite LinkToSysext (new param), update UnlinkFromSysext, GetInstalledVersions, GetActiveVersion, RemoveAllVersions; remove UpdateSymlink if unused
sysext/manager_test.go	Update existing tests, add TestSysextLinkName, add no-CurrentSymlink cases, remove UpdateSymlink tests if function removed
updex/install.go	Remove staging symlink creation, pass targetFile to LinkToSysext, add legacy cleanup
yeti/OVERVIEW.md	Update data flow description
yeti/config-reference.md	Mark CurrentSymlink as deprecated

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Potential risks and edge cases

1. Existing deployments with staging symlinks: The cleanup in installTransfer (step 7) removes them on next update. RemoveAllVersions handles them on disable. No migration step needed.

2. Transfer files without CurrentSymlink: Work correctly — this is the primary goal. No warning emitted.

3. Transfer files with CurrentSymlink: Still parsed (no config error), but the value is only used for best-effort removal of legacy staging symlinks. No functionality depends on it.

4. SysextLinkName correctness: Relies on t.Component (derived from filename, always set) and filepath.Ext(t.Target.MatchPattern) (always .raw for sysexts, since target patterns are the decompressed form). If a future target type uses a different extension, it still works correctly.

5. LinkToSysext signature change: This is an exported function. External callers must update. Acceptable as a breaking change with a minor version bump given the SDK's maturity level.

6. GetInstalledVersions / GetActiveVersion reading /var/lib/extensions/: In test environments, SysextDir is a const (/var/lib/extensions). Tests that need to verify current-version resolution via symlink will need to either use a temp dir override or test only the fallback path. Consider making SysextDir overridable for testing (e.g., a package-level variable or a parameter).

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Suggested implementation order

1. Add SysextLinkName() + tests (pure addition, no breakage)
2. Rewrite LinkToSysext signature and implementation
3. Update UnlinkFromSysext to use derived name
4. Update GetInstalledVersions and GetActiveVersion to read sysext dir symlink
5. Update RemoveAllVersions for legacy cleanup
6. Update updex/install.go (remove staging symlink, pass targetFile, add cleanup)
7. Remove UpdateSymlink if unused
8. Update all tests
9. Update docs

[bketelsen]

— Automated by Yeti —

Plan Review

1. The cleanup step in installTransfer is unsafe as written. Target.Path defaults to /var/lib/extensions, not a separate staging dir, so os.Remove(filepath.Join(transfer.Target.Path, transfer.Target.CurrentSymlink)) can delete the live sysext link you just created instead of a redundant staging link. See config/transfer.go and updex/install.go. The plan needs an explicit rule for when a “staging” cleanup is valid, especially when Target.Path == sysext.SysextDir.

2. The plan does not fully satisfy requirement 3 for legacy symlink cleanup. Today LinkToSysext creates /var/lib/extensions/<CurrentSymlink> directly, and after the change UnlinkFromSysext would remove only the derived <name>.raw. If a transfer still has a legacy CurrentSymlink value that differs from the derived name, the old /var/lib/extensions/<CurrentSymlink> link will be left behind on update/disable. See sysext/manager.go and sysext/manager.go.

3. Step 7 is too dangerous: “iterate entries looking for symlinks and remove them all” can delete unrelated component links. RemoveAllVersions operates on whatever Target.Path is, and that may be a shared directory. Cleanup must be limited to the component’s known legacy and derived symlink names, not every symlink in the directory. See sysext/manager.go and config/transfer.go.

4. The proposed SysextLinkName derivation is based on assumptions the codebase does not enforce. Target.MatchPattern only has to be present; nothing requires _@v specifically, and Target.Patterns() supports multiple alternatives. A helper that just strips from _@v is brittle for patterns like name-@v.raw or any future variant. See config/transfer.go and sysext/manager.go.

5. The test plan is under-scoped and partly not implementable with the current seams. GetInstalledVersions/GetActiveVersion would need to read /var/lib/extensions and /run/extensions, but those paths are hardcoded (SysextDir is a const, /run/extensions is inline), so “mock that path” is not currently possible without refactoring. Also, feature-level tests and helpers currently assume CurrentSymlink exists and use it to simulate active/current state. See sysext/manager.go, sysext/manager.go, updex/features_test.go, and updex/test_helpers_test.go.

6. The plan understates the public API and documentation impact. sysext.LinkToSysext is exported, its signature is documented, and CurrentSymlink appears in user-facing docs beyond yeti/OVERVIEW.md and yeti/config-reference.md. If the signature changes or CurrentSymlink becomes deprecated, yeti/sdk-api.md and README.md also need updates.

Open question: the issue description says updex “will fail to download” without CurrentSymlink, but the current implementation only warns on LinkToSysext failure and still returns success from install. See updex/install.go. The plan should be explicit about whether the goal is to preserve that non-fatal behavior while fixing activation/linking.

[bsherman]

updex should function properly with or without the existence of a CurrentSymlink directive in the transfer file. No warning should be given if the CurrentSymlink directive is absent. Only if it is present should updex look for and remove the symlink which may have been been perviously created by updex previously.

regarding step 1 of the implementation plan, the SysextLinkName should not fallback to CurrentSymlink as it is not expected to exist. Avoid guessing and pattern matching of the package name, instead use only the transfer file's name (eg, foo.transfer to construct a link name foo.<ext> (do use the extension, not including compression, from the MatchPattern).

[bketelsen]

— Automated by Yeti —

Note

The original plan derived SysextLinkName by parsing the MatchPattern for _@v and stripping everything after it. Per the feedback, the updated plan uses t.Component (from the .transfer filename) instead — this is simpler, more reliable, and doesn't require pattern-matching heuristics. The extension is taken from filepath.Ext(t.Target.MatchPattern) rather than hardcoding .raw, which handles any future extension types while ignoring compression suffixes (target patterns are always decompressed).