Mount host kernel modules in build pods for in-tree dependency resolution by TomerNewman · Pull Request #1222 · kubernetes-sigs/kernel-module-management

TomerNewman · 2026-01-22T13:13:57Z

Enable OOT modules to depend on in-tree modules by mounting the host's /lib/modules into pods at /host/lib/modules. The /host prefix avoids conflicts with Kaniko during builds.

Also removing /usr/lib/modules from worker and build pods.

Worker pods get both paths (/lib/modules and /host/lib/modules) for backward compatibility.

Docs in docs/mkdocs/documentation/kmod_image.md updated with usage example.

/cc @ybettan @yevgeny-shnaidman

k8s-ci-robot · 2026-01-22T13:14:04Z

[APPROVALNOTIFIER] This PR is APPROVED

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codecov-commenter · 2026-01-22T13:18:17Z

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 73.75%. Comparing base (fa23a9b) to head (93fa153).
⚠️ Report is 345 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1222      +/-   ##
==========================================
- Coverage   79.09%   73.75%   -5.34%     
==========================================
  Files          51       66      +15     
  Lines        5109     4611     -498     
==========================================
- Hits         4041     3401     -640     
- Misses        882     1048     +166     
+ Partials      186      162      -24

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yevgeny-shnaidman · 2026-01-22T14:26:25Z

internal/pod/workerpodmanager.go

 		{
 			Name:      volNameLibModules,
-			MountPath: "/lib/modules",
+			MountPath: "/host/lib/modules",


Why do we need to change the VolumeMount for worker pod? If we change it, then the current code won't work, i think

I changed it for consistency, Im reviewing it now since the e2e test failed.

TomerNewman · 2026-01-22T14:30:37Z

/hold

TomerNewman · 2026-01-26T14:05:49Z

docs/mkdocs/documentation/kmod_image.md

 `modprobe` can then follow that link and load the in-tree dependencies as needed.

-In the example below, we use `host` as the symbolic link name under `/opt/usr/lib/modules/[kernel-version]`:
+In the example below, we use `host` as the symbolic link name under `/opt/lib/modules/[kernel-version]`:


This doc mistake is not related, but still thought to fix it here

TomerNewman · 2026-01-27T07:57:57Z

/unhold

ybettan · 2026-01-27T11:03:21Z

internal/pod/workerpodmanager.go

+		{
+			Name: "host-lib-modules",
+			VolumeSource: v1.VolumeSource{
+				HostPath: &v1.HostPathVolumeSource{
+					Path: "/lib/modules",
+					Type: &hostPathDirectory,
+				},
+			},
+		},
+		{
+			Name: "host-usr-lib-modules",
+			VolumeSource: v1.VolumeSource{
+				HostPath: &v1.HostPathVolumeSource{
+					Path: "/usr/lib/modules",
+					Type: &hostPathDirectory,
+				},
+			},
+		},


Why do we need additional volumes? They are already defined here.

Because I made the Build pod use /host/lib/modules to avoid Kaniko conflicts (kaniko extracts the base image into /).
The image Dockerfile create symlinks pointing there, so worker pod needs the same mount for those symlinks to work.

@TomerNewman i think we don't need to define the volumes twice, we can just define a new VolumeMount for the same volume and mount it into the /host/lib/modules/ etc'

Oh by bad, made a mix up with the volumeMount, fixing it now

ybettan · 2026-01-27T11:05:31Z

internal/pod/workerpodmanager.go

+		{
+			Name:      "host-lib-modules",
+			MountPath: "/host/lib/modules",
+			ReadOnly:  true,
+		},
+		{
+			Name:      "host-usr-lib-modules",
+			MountPath: "/host/usr/lib/modules",
+			ReadOnly:  true,
+		},


Why do we need to mount it to 2 different paths? We already mount them at /lib/modules and /usr/lib/modules.
If we change it we need to make sure to also update the docs changes in this PR and the commit message.

Answered here.

Np

ybettan · 2026-01-27T11:06:18Z

internal/buildsign/resource/volumes.go

+		{
+			Name:      "lib-modules",
+			ReadOnly:  true,
+			MountPath: "/host/lib/modules",
+		},
+		{
+			Name:      "usr-lib-modules",
+			ReadOnly:  true,
+			MountPath: "/host/usr/lib/modules",
+		},


Why don't we mount it to the same location as the worker pods instead of setting a new paths and then adding this new path to the worker pod as well and in addition keep the old "legacy" path?

We can't mount to /lib/modules in build pods because Kaniko extracts the base image to /, which conflicts with a mount in /lib/modules.

ybettan · 2026-02-02T08:08:35Z

internal/buildsign/resource/volumes.go

+			VolumeSource: v1.VolumeSource{
+				HostPath: &v1.HostPathVolumeSource{
+					Path: "/lib/modules",
+					Type: &hostPathDirectory,


Can we do the same as here https://github.com/kubernetes-sigs/kernel-module-management/pull/1222/changes#diff-98eead772f708d7e017665ada1b681377fd492ff91aa5b5ba17bb5f52375ececR175 and remove the hostPathDirectory variable which is only used here?

Enable OOT modules to depend on in-tree modules by mounting the host's /lib/modules into pods at /host/lib/modules. The /host prefix avoids conflicts with Kaniko during builds. Also removing /usr/lib/modules mount from build and worker pods. Worker pods get both paths (/lib/modules and /host/lib/modules) for backward compatibility. Docs in docs/mkdocs/documentation/kmod_image.md updated with usage example.

ybettan · 2026-02-05T10:06:25Z

I am happy with this PR when @yevgeny-shnaidman is.

yevgeny-shnaidman · 2026-02-05T14:17:38Z

/lgtm

k8s-ci-robot requested review from ybettan and yevgeny-shnaidman January 22, 2026 13:14

k8s-ci-robot added cncf-cla: yes Indicates the PR's author has signed the CNCF CLA. approved Indicates a PR has been approved by an approver from all required OWNERS files. size/M Denotes a PR that changes 30-99 lines, ignoring generated files. labels Jan 22, 2026

TomerNewman changed the title ~~Mount host kernel modules in build pods for in-tree dependency resolu…~~ Mount host kernel modules in build pods for in-tree dependency resolution Jan 22, 2026

TomerNewman force-pushed the mount-host-modules-in-build-pod branch from 056a9b5 to ee9b60f Compare January 22, 2026 13:15

TomerNewman changed the title ~~Mount host kernel modules in build pods for in-tree dependency resolution~~ Mount host kernel modules in build pods for in-tree dependency resolution [WIP] Jan 22, 2026

yevgeny-shnaidman reviewed Jan 22, 2026

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k8s-ci-robot added the do-not-merge/hold Indicates that a PR should not merge because someone has issued a /hold command. label Jan 22, 2026

TomerNewman force-pushed the mount-host-modules-in-build-pod branch from ee9b60f to 5de5373 Compare January 26, 2026 12:49

k8s-ci-robot added size/L Denotes a PR that changes 100-499 lines, ignoring generated files. and removed size/M Denotes a PR that changes 30-99 lines, ignoring generated files. labels Jan 26, 2026

TomerNewman commented Jan 26, 2026

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k8s-ci-robot removed the do-not-merge/hold Indicates that a PR should not merge because someone has issued a /hold command. label Jan 27, 2026

TomerNewman changed the title ~~Mount host kernel modules in build pods for in-tree dependency resolution [WIP]~~ Mount host kernel modules in build pods for in-tree dependency resolution Jan 27, 2026

ybettan reviewed Jan 27, 2026

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TomerNewman force-pushed the mount-host-modules-in-build-pod branch 4 times, most recently from bfe60ca to 0a3376c Compare January 29, 2026 10:18

k8s-ci-robot added size/M Denotes a PR that changes 30-99 lines, ignoring generated files. and removed size/L Denotes a PR that changes 100-499 lines, ignoring generated files. labels Jan 29, 2026

TomerNewman force-pushed the mount-host-modules-in-build-pod branch from 0a3376c to 7559ca5 Compare January 29, 2026 10:22

ybettan reviewed Feb 2, 2026

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TomerNewman force-pushed the mount-host-modules-in-build-pod branch 2 times, most recently from 63831e1 to a1ea805 Compare February 2, 2026 08:34

TomerNewman force-pushed the mount-host-modules-in-build-pod branch from a1ea805 to 93fa153 Compare February 2, 2026 08:40

k8s-ci-robot assigned yevgeny-shnaidman Feb 5, 2026

k8s-ci-robot added the lgtm "Looks good to me", indicates that a PR is ready to be merged. label Feb 5, 2026

k8s-ci-robot merged commit d8e8410 into kubernetes-sigs:main Feb 5, 2026
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