[release-4.20] OCPBUGS-65898: fixes systemd unit creation for empty units

[openshift-cherrypick-robot]

This is an automated cherry-pick of #5086

/assign sdodson

[openshift-ci-robot]

@openshift-cherrypick-robot: Jira Issue OCPBUGS-56648 has been cloned as Jira Issue OCPBUGS-65898. Will retitle bug to link to clone.
/retitle [release-4.20] OCPBUGS-65898: fixes systemd unit creation for empty units

In response to this:

This is an automated cherry-pick of #5086

/assign sdodson

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[openshift-ci-robot]

@openshift-cherrypick-robot: This pull request references Jira Issue OCPBUGS-65898, which is invalid:

• release note text must be set and not match the template OR release note type must be set to "Release Note Not Required". For more information you can reference the OpenShift Bug Process.

Comment /jira refresh to re-evaluate validity if changes to the Jira bug are made, or edit the title of this pull request to link to a different bug.

The bug has been updated to refer to the pull request using the external bug tracker.

In response to this:

This is an automated cherry-pick of #5086

/assign sdodson

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[sdodson]

/assign @cheesesashimi

[isabella-janssen]

/lgtm
/label backport-risk-assessed

Looks like a clean backport to me!

[openshift-ci]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: isabella-janssen, openshift-cherrypick-robot

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[cheesesashimi]

/jira refresh

[openshift-ci-robot]

@cheesesashimi: This pull request references Jira Issue OCPBUGS-65898, which is valid. The bug has been moved to the POST state.

7 validation(s) were run on this bug

• bug is open, matching expected state (open)
• bug target version (4.20.z) matches configured target version for branch (4.20.z)
• bug is in the state New, which is one of the valid states (NEW, ASSIGNED, POST)
• release note type set to "Release Note Not Required"
• dependent bug Jira Issue OCPBUGS-56648 is in the state Verified, which is one of the valid states (VERIFIED, RELEASE PENDING, CLOSED (ERRATA), CLOSED (CURRENT RELEASE), CLOSED (DONE), CLOSED (DONE-ERRATA))
• dependent Jira Issue OCPBUGS-56648 targets the "4.21.0" version, which is one of the valid target versions: 4.21.0
• bug has dependents

Requesting review from QA contact:
/cc @sergiordlr

In response to this:

/jira refresh

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[sergiordlr]

Verified using IPI on AWS

1. Apply a MC with an enabled empty unit

apiVersion: machineconfiguration.openshift.io/v1
kind: MachineConfig
metadata:
  labels:
    machineconfiguration.openshift.io/role: worker
  name: mc-unit-22
spec:
  config:
    ignition:
      version: 2.2.0
    systemd:
      units:
      - name: my22unit.service
        enable: true

2. Wait for the configuration to be applied. No degradation happens
3. Check the logs

2025-12-05T10:02:50.927719111+00:00 stderr F I1205 10:02:50.927676    2696 file_writers.go:330] Unit "my22unit.service" has no content, skipping write
2025-12-05T10:02:50.927719111+00:00 stderr F I1205 10:02:50.927699    2696 update.go:2140] Could not enable unit "my22unit.service", because it has no contents, skipping

4. No unit is created

$ oc debug node/ip-10-0-29-169.us-east-2.compute.internal -q -- chroot /host systemctl status my22unit.service
Unit my22unit.service could not be found.
error: non-zero exit code from debug container

5. Repeat verification steps in master pool. No issues found.

The following tests were executed and passed:

passed: (14m18s) 2025-12-05T10:33:47 "[sig-mco] MCO NodeDisruptionPolicy Author:rioliu-NonPreRelease-Longduration-High-73411-NodeDisruptionPolicy units with multiple actions [Disruptive] [Serial]"
passed: (25m30s) 2025-12-05T10:59:17 "[sig-mco] MCO Author:sregidor-Longduration-NonPreRelease-High-47008-Config Drift. Dropin file. [Serial]"
passed: (18m29s) 2025-12-05T11:17:46 "[sig-mco] MCO NodeDisruptionPolicy Author:rioliu-NonPreRelease-Longduration-High-73413-[P2] NodeDisruptionPolicy units with action Reboot [Disruptive] [Serial]"
passed: (19m30s) 2025-12-05T11:37:16 "[sig-mco] MCO Author:sregidor-NonPreRelease-Longduration-Medium-56614-[P2][OnCLayer] Create unit with content and mask=true[Disruptive] [Serial]"
passed: (3m32s) 2025-12-05T11:40:48 "[sig-mco] MCO NodeDisruptionPolicy Author:rioliu-NonPreRelease-High-73414-[P1] NodeDisruptionPolicy units with action None [Disruptive] [Serial]"
passed: (25m35s) 2025-12-05T12:06:23 "[sig-mco] MCO Author:sregidor-Longduration-NonPreRelease-High-47009-Config Drift. New Service Unit. [Serial]"

/label qe-approved
/label cherry-pick-approved
/verified by @sergiordlr

[openshift-ci-robot]

@sergiordlr: This PR has been marked as verified by @sergiordlr.

In response to this:

Verified using IPI on AWS

1. Apply a MC with an enabled empty unit

apiVersion: machineconfiguration.openshift.io/v1
kind: MachineConfig
metadata:
 labels:
   machineconfiguration.openshift.io/role: worker
 name: mc-unit-22
spec:
 config:
   ignition:
     version: 2.2.0
   systemd:
     units:
     - name: my22unit.service
       enable: true

2. Wait for the configuration to be applied. No degradation happens
3. Check the logs

2025-12-05T10:02:50.927719111+00:00 stderr F I1205 10:02:50.927676    2696 file_writers.go:330] Unit "my22unit.service" has no content, skipping write
2025-12-05T10:02:50.927719111+00:00 stderr F I1205 10:02:50.927699    2696 update.go:2140] Could not enable unit "my22unit.service", because it has no contents, skipping

4. No unit is created

$ oc debug node/ip-10-0-29-169.us-east-2.compute.internal -q -- chroot /host systemctl status my22unit.service
Unit my22unit.service could not be found.
error: non-zero exit code from debug container

5. Repeat verification steps in master pool. No issues found.

The following tests were executed and passed:

passed: (14m18s) 2025-12-05T10:33:47 "[sig-mco] MCO NodeDisruptionPolicy Author:rioliu-NonPreRelease-Longduration-High-73411-NodeDisruptionPolicy units with multiple actions [Disruptive] [Serial]"
passed: (25m30s) 2025-12-05T10:59:17 "[sig-mco] MCO Author:sregidor-Longduration-NonPreRelease-High-47008-Config Drift. Dropin file. [Serial]"
passed: (18m29s) 2025-12-05T11:17:46 "[sig-mco] MCO NodeDisruptionPolicy Author:rioliu-NonPreRelease-Longduration-High-73413-[P2] NodeDisruptionPolicy units with action Reboot [Disruptive] [Serial]"
passed: (19m30s) 2025-12-05T11:37:16 "[sig-mco] MCO Author:sregidor-NonPreRelease-Longduration-Medium-56614-[P2][OnCLayer] Create unit with content and mask=true[Disruptive] [Serial]"
passed: (3m32s) 2025-12-05T11:40:48 "[sig-mco] MCO NodeDisruptionPolicy Author:rioliu-NonPreRelease-High-73414-[P1] NodeDisruptionPolicy units with action None [Disruptive] [Serial]"
passed: (25m35s) 2025-12-05T12:06:23 "[sig-mco] MCO Author:sregidor-Longduration-NonPreRelease-High-47009-Config Drift. New Service Unit. [Serial]"

/label qe-approved
/label cherry-pick-approved
/verified by @sergiordlr

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the openshift-eng/jira-lifecycle-plugin repository.

[openshift-ci-robot]

@openshift-cherrypick-robot: This pull request references Jira Issue OCPBUGS-65898, which is valid.

7 validation(s) were run on this bug

• bug is open, matching expected state (open)
• bug target version (4.20.z) matches configured target version for branch (4.20.z)
• bug is in the state POST, which is one of the valid states (NEW, ASSIGNED, POST)
• release note type set to "Release Note Not Required"
• dependent bug Jira Issue OCPBUGS-56648 is in the state Verified, which is one of the valid states (VERIFIED, RELEASE PENDING, CLOSED (ERRATA), CLOSED (CURRENT RELEASE), CLOSED (DONE), CLOSED (DONE-ERRATA))
• dependent Jira Issue OCPBUGS-56648 targets the "4.21.0" version, which is one of the valid target versions: 4.21.0
• bug has dependents

Requesting review from QA contact:
/cc @sergiordlr

In response to this:

This is an automated cherry-pick of #5086

/assign sdodson

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the openshift-eng/jira-lifecycle-plugin repository.

[openshift-ci]

@openshift-cherrypick-robot: The following test failed, say /retest to rerun all failed tests or /retest-required to rerun all mandatory failed tests:

Test name	Commit	Details	Required	Rerun command
ci/prow/bootstrap-unit	702dd8b	link	false	/test bootstrap-unit

Full PR test history. Your PR dashboard.

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[openshift-ci-robot]

/retest-required

Remaining retests: 0 against base HEAD 5fe9249 and 2 for PR HEAD 702dd8b in total

[openshift-ci-robot]

@openshift-cherrypick-robot: Jira Issue Verification Checks: Jira Issue OCPBUGS-65898
✔️ This pull request was pre-merge verified.
✔️ All associated pull requests have merged.
✔️ All associated, merged pull requests were pre-merge verified.

Jira Issue OCPBUGS-65898 has been moved to the MODIFIED state and will move to the VERIFIED state when the change is available in an accepted nightly payload. 🕓

In response to this:

This is an automated cherry-pick of #5086

/assign sdodson

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the openshift-eng/jira-lifecycle-plugin repository.