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internal/partitioners: add sfdisk partitioning backend - #2337
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| Check name | Status | Explanation | Resolution |
|---|---|---|---|
| Linked Issues check |  |
Issue #1926 requires an sfdisk backend with an API equivalent to sgdisk and a backend-selection kernel argument. The new partitioners.DeviceManager, internal/partitioners/sfdisk, and `PartitionerB… |
Add a link-time configurable default backend in internal/distro. Make ignition.partitioner override that default. Add automated tests for the configured default and the kernel-argument override. |
| Docstring Coverage | |
Docstring coverage is 26.47% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 68 functions across 13 files. (1 skipped:… | Write docstrings for the functions missing them to satisfy the coverage threshold. |
| Commit Message Convention | |
The PR still contains one non-merge commit that violates the convention: 496d8786c02f1aecec284930210c741b7ae9f1de has subject fixup! internal/partitioners/sfdisk: add sfdisk partitioner backend. T… |
Squash commit 496d8786c02f1aecec284930210c741b7ae9f1de into its target commit, or reword it to a valid subject such as internal/partitioners/sfdisk: fix <lowercase imperative description> with no trailing period. |
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Check name Status Explanation Title check The title follows the required format, uses the subsystem prefix "internal/partitioners", starts the description in lowercase, uses imperative mood, and accurately describes the main change. Description check The description is directly related to the changes. It explains the opt-in sfdisk backend, backend selection, shared partitioning changes, testing updates, and release notes. Out of Scope Changes check The changes remain connected to issue #1926. They add the sfdisk backend, shared partitioner API, backend dispatch, partition metadata handling, validator fallback, backend test variants, and release …Full details: Out of Scope Changes check
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Explanation
The changes remain connected to issue
#1926. They add the sfdisk backend, shared partitioner API, backend dispatch, partition metadata handling, validator fallback, backend test variants, and release documentation. No unrelated change is demonstrated.
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Full details: Linked Issues check
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Explanation
Issue
#1926requires an sfdisk backend with an API equivalent to sgdisk and a backend-selection kernel argument. The newpartitioners.DeviceManager,internal/partitioners/sfdisk, andPartitionerBackend()implement these requirements. The issue proposal also requires a compile-time default that the kernel argument can override.PartitionerBackend()has a fixedsgdiskfallback and does not expose a link-time configurable default. The later default switch, deprecation, removal, and stream rollout are future steps and are not required for this PR.Resolution
Add a link-time configurable default backend in
internal/distro. Makeignition.partitioneroverride that default. Add automated tests for the configured default and the kernel-argument override.
Full details: Docstring Coverage
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Explanation
Docstring coverage is 26.47% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 68 functions across 13 files. (1 skipped: 1 unsupported.)
Resolution
Write docstrings for the functions missing them to satisfy the coverage threshold.
Full details: Commit Message Convention
-
Explanation
The PR still contains one non-merge commit that violates the convention:
496d8786c02f1aecec284930210c741b7ae9f1dehas subjectfixup! internal/partitioners/sfdisk: add sfdisk partitioner backend. Thefixup!prefix prevents the requiredsubsystem: lowercase imperative descriptionformat. The other six non-merge subjects use valid lowercase imperative descriptions and have no trailing periods.Resolution
Squash commit
496d8786c02f1aecec284930210c741b7ae9f1deinto its target commit, or reword it to a valid subject such asinternal/partitioners/sfdisk: fix <lowercase imperative description>with no trailing period.
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Binary size report (
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| Size | |
|---|---|
Base (main) |
33MiB |
| PR (#2337) | 33MiB |
| Delta | +66KiB (0.19%) |
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Inline comments:
Review comments at @internal/partitioners/sfdisk/sfdisk.go:
- Around line 416-419: Assign explicit partition numbers to number-0 entries in
op.parts order before buildScript sorts them, using the same first-free
numbering rule as the stage and preserving numbers already assigned to explicit
entries. This keeps sfdisk’s output row numbers mapped to the correct partitions
by getRealStartAndSize.
- Around line 155-162: Update readExistingPartitions to return an error when
sfdisk --dump fails, except when the failure explicitly identifies that no
partition table exists; do not treat other command failures as an empty table.
Also reject a successfully dumped label other than gpt when op.wipe is false.
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📒 Files selected for processing (12)
config/shared/errors/errors.godocs/release-notes.mdinternal/distro/distro.gointernal/exec/stages/disks/partitions.gointernal/partitioners/partitioners.gointernal/partitioners/sfdisk/sfdisk.gointernal/partitioners/sfdisk/sfdisk_test.gointernal/partitioners/sfdisk/zap.gointernal/partitioners/sfdisk/zap_linux.gointernal/partitioners/sfdisk/zap_other.gointernal/partitioners/sgdisk/sgdisk.gotests/validator.go
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🧰 Additional context used
📚 Code guidelines (1)
AGENTS.md — auto-discovered
📓 Path-based instructions (5)
Execution stages are fixed (fetch-offline, fetch, disks, mount, files, umount).
⚙️ CodeRabbit configuration file
Files:
internal/exec/stages/disks/partitions.go
The config/ directory is the frontend stable library API consumed by external programs (e.g., Butane).
⚙️ CodeRabbit configuration file
Files:
config/shared/errors/errors.go
Blackbox integration tests.
⚙️ CodeRabbit configuration file
Files:
tests/validator.go
Documentation served via GitHub Pages/Jekyll.
⚙️ CodeRabbit configuration file
Files:
docs/release-notes.md
Source excerpt: **License header**: Required on all `.go` files (Apache 2.0, 13-line header)
📄 CodeRabbit inference engine (AGENTS.md)
Files:
config/shared/errors/errors.gointernal/partitioners/sfdisk/zap_other.gointernal/partitioners/sfdisk/zap.gointernal/distro/distro.gointernal/partitioners/sfdisk/zap_linux.gointernal/partitioners/partitioners.gotests/validator.gointernal/partitioners/sfdisk/sfdisk_test.gointernal/partitioners/sfdisk/sfdisk.gointernal/exec/stages/disks/partitions.gointernal/partitioners/sgdisk/sgdisk.go
🪛 ast-grep (0.45.3)
internal/exec/stages/disks/partitions.go
[error] 576-576: An argument passed to exec.Command/exec.CommandContext is built by concatenating a string literal with dynamic input. If that input is attacker-controlled (and especially when the command is a shell such as sh -c/bash -c), this enables OS command injection. Pass untrusted data as separate, fixed arguments instead of interpolating it into a command string, avoid invoking a shell, and validate/escape the input where a shell is unavoidable.
Context: exec.Command(distro.PartxCmd(), "--"+op, "--nr", fmt.Sprint(partNr), blockDevResolved)
Note: [CWE-78] Improper Neutralization of Special Elements used in an OS Command ('OS Command Injection').
(command-injection-exec-concat-arg-go)
🔇 Additional comments (11)
internal/partitioners/partitioners.go (1)
1-52: LGTM!internal/distro/distro.go (1)
157-188: LGTM!internal/partitioners/sgdisk/sgdisk.go (1)
122-197: LGTM!config/shared/errors/errors.go (1)
95-95: LGTM!internal/partitioners/sfdisk/sfdisk_test.go (1)
1-402: LGTM!internal/partitioners/sfdisk/zap.go (1)
1-154: LGTM!internal/partitioners/sfdisk/zap_linux.go (1)
1-59: LGTM!internal/partitioners/sfdisk/zap_other.go (1)
1-33: LGTM!internal/exec/stages/disks/partitions.go (1)
44-51: LGTM!Also applies to: 525-532, 571-588
tests/validator.go (1)
45-80: LGTM!Also applies to: 135-181
docs/release-notes.md (1)
13-15: LGTM!
Two data-integrity fixes raised in review of PR coreos#2337: - readExistingPartitions no longer treats every "sfdisk --dump" failure as a blank disk. Only the explicit "does not contain a recognized partition table" result is an empty table; any other error is returned. Because this backend rewrites the whole table, swallowing a transient or corrupt-table read would silently drop every preserved partition. Also refuse to rewrite a non-gpt label as gpt unless the table is being wiped. - mergePartitions assigns real numbers to auto-numbered (Number == 0) entries in op.parts order with the first-free rule, before buildScript sorts them by tier. sfdisk numbers bare script lines in script order, so without this the output rows did not line up with the numbers the disks stage assigns and ParseOutput mapped geometry onto the wrong partition, swapping start/size between partitions. Adds TestMergePartitionsAssignsAutoNumbersInOrder covering the second fix.
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I rewrote the commits to replace the vendor-specific |
Two data-integrity fixes raised in review of PR coreos#2337: - readExistingPartitions no longer treats every "sfdisk --dump" failure as a blank disk. Only the explicit "does not contain a recognized partition table" result is an empty table; any other error is returned. Because this backend rewrites the whole table, swallowing a transient or corrupt-table read would silently drop every preserved partition. Also refuse to rewrite a non-gpt label as gpt unless the table is being wiped. - mergePartitions assigns real numbers to auto-numbered (Number == 0) entries in op.parts order with the first-free rule, before buildScript sorts them by tier. sfdisk numbers bare script lines in script order, so without this the output rows did not line up with the numbers the disks stage assigns and ParseOutput mapped geometry onto the wrong partition, swapping start/size between partitions. Adds TestMergePartitionsAssignsAutoNumbersInOrder covering the second fix.
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Two data-integrity fixes raised in review of PR coreos#2337: - readExistingPartitions no longer treats every "sfdisk --dump" failure as a blank disk. Only the explicit "does not contain a recognized partition table" result is an empty table; any other error is returned. Because this backend rewrites the whole table, swallowing a transient or corrupt-table read would silently drop every preserved partition. Also refuse to rewrite a non-gpt label as gpt unless the table is being wiped. - mergePartitions assigns real numbers to auto-numbered (Number == 0) entries in op.parts order with the first-free rule, before buildScript sorts them by tier. sfdisk numbers bare script lines in script order, so without this the output rows did not line up with the numbers the disks stage assigns and ParseOutput mapped geometry onto the wrong partition, swapping start/size between partitions. Adds TestMergePartitionsAssignsAutoNumbersInOrder covering the second fix.
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Rolv-Apneseth
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Some very minor things, but LGTM. Though I'm not very familiar with Go or sgdisk/sfdisk to be honest.
I did notice, however, that sfdisk(8) has a --json <device> flag. Would that be helpful in sfdisk.go? Maybe a worth follow-up if so.
Introduce a DeviceManager interface abstracting partition-table operations so the disks stage can target multiple partitioner backends. Move the existing sgdisk implementation under internal/partitioners/sgdisk and adapt it to the interface: the shared Partition and Output types now live in the partitioners package, and the pretend-output parsing (formerly parseSgdiskPretend in the disks stage) moves into the backend as ParseOutput. The disks stage selects its backend through getDeviceManager, which for now always returns sgdisk, preserving existing behavior. Assisted-by: AI tooling
Add an sfdisk-based DeviceManager implementation as an alternative to sgdisk, motivated by sgdisk losing upstream support and no longer being shipped in the target OSes. sfdisk rewrites the whole partition table from a script, so the backend reports WritesCompleteTable and re-lists preserved partitions (including their GPT attribute bits and raw labels) on every commit to avoid losing state. Pretend and commit are pinned to the on-disk label-id, first-lba and last-lba so repeated provisioning is idempotent and does not churn disk geometry or the disk GUID. Partition names are encoded/decoded in sfdisk's quoted \xHH script form so arbitrary label bytes round-trip. Table wipes zap the GPT/MBR structures directly (sfdisk has no sgdisk --zap-all equivalent that leaves filesystem signatures intact), matching sgdisk semantics; a build-tagged helper falls back to the file size when block-device ioctls are unavailable. distro.SfdiskCmd exposes the sfdisk binary path; backend selection is wired up in a following commit. Assisted-by: AI tooling
Add distro.PartitionerBackend, which reads the "ignition.partitioner" kernel argument (overridable with the IGNITION_PARTITIONER environment variable for testing) and defaults to sgdisk. The disks stage's getDeviceManager dispatches to the sfdisk backend when ignition.partitioner=sfdisk and otherwise keeps using sgdisk, so existing deployments are unaffected unless they opt in. Assisted-by: AI tooling
The blackbox validator inspected partitions exclusively through sgdisk. Fall back to sfdisk --list/--part-* in getPartitionSet and getPartitionInfo when sgdisk is unavailable, so the suite can validate disks partitioned by either backend. Assisted-by: AI tooling
Assisted-by: AI tooling
The blackbox suite already fans each test out across every config spec version in register.Register. Extend that generation to also cover the partitioner backends: any test whose config drives Ignition's disks stage is now registered once per backend (sgdisk and sfdisk), selected via the IGNITION_PARTITIONER environment variable that runIgnition already propagates. The backend is recorded in the test name (e.g. .../partition.create_3.0.0/sfdisk) so variants are individually addressable with -test.run. Tests that never invoke a partitioner (files, users, systemd units, ...) are detected by the absence of a storage.disks section and are registered once, so the fan-out does not needlessly double the suite. A backend variant is skipped when its tool is not installed. Because fixtures assert the expected partition table independently of the backend, and the validator reads it with an independent tool, this asserts sfdisk and sgdisk produce identical results from the same configs without any new fixtures. Assisted-by: AI tooling
Two data-integrity fixes raised in review of PR coreos#2337: - readExistingPartitions no longer treats every "sfdisk --dump" failure as a blank disk. Only the explicit "does not contain a recognized partition table" result is an empty table; any other error is returned. Because this backend rewrites the whole table, swallowing a transient or corrupt-table read would silently drop every preserved partition. Also refuse to rewrite a non-gpt label as gpt unless the table is being wiped. - mergePartitions assigns real numbers to auto-numbered (Number == 0) entries in op.parts order with the first-free rule, before buildScript sorts them by tier. sfdisk numbers bare script lines in script order, so without this the output rows did not line up with the numbers the disks stage assigns and ParseOutput mapped geometry onto the wrong partition, swapping start/size between partitions. Adds TestMergePartitionsAssignsAutoNumbersInOrder covering the second fix.
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Thanks! All three addressed, folded into the existing commits after the Error message: applied your wording verbatim. Agreed on reporting — the invalid value case is the nasty one, someone On --json: I poked at it locally. It's great for --dump (everything we One thing I stumbled on while testing: sfdisk emits attrs space-separated |
Summary
Add an sfdisk partitioning backend as an alternative to sgdisk,
selectable via the
ignition.partitionerkernel argument. This ismotivated by sgdisk (gptfdisk) losing upstream support and no longer
being shipped in the target OSes (Fedora CoreOS, RHEL CoreOS, Flatcar).
sgdisk remains the default; sfdisk is opt-in with
ignition.partitioner=sfdisk, so existing deployments are unaffected.This supersedes #1929 with a cleaned-up commit history. The functional
code is the same, restructured into reviewable, individually-building
commits. The local-development-only integration harness and manual
comparison script from #1929 are intentionally not carried over.
Changes
internal/partitioners: newDeviceManagerinterface abstractingpartition-table operations; the shared
Partition/Outputtypes andthe existing sgdisk implementation move here (sgdisk's pretend-output
parsing becomes
ParseOutput).internal/partitioners/sfdisk: new sfdisk backend. It rewrites thewhole partition table from a script, re-listing preserved partitions
(including GPT attribute bits and raw labels) and pinning label-id /
first-lba / last-lba so reprovisioning is idempotent and does not
churn geometry or the disk GUID. Labels round-trip through sfdisk's
quoted
\xHHscript form. Table wipes zap GPT/MBR structures directly(matching
sgdisk --zap-allsemantics while leaving filesystemsignatures to the filesystems stage).
internal/distro:PartitionerBackend()readsignition.partitioner(overridable via
IGNITION_PARTITIONERfor testing), defaulting tosgdisk;
SfdiskCmd()exposes the binary path.internal/exec/stages/disks:getDeviceManager()dispatches to theselected backend.
tests: blackbox disk validator falls back to sfdisk when sgdisk isunavailable.
docs: release note.Resolves #1926
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