Document kernel version requirements for Linux #47363

pacoxu · 2024-08-05T10:55:57Z

Description

Starting from kubernetes/kubernetes#116799, I collected a lot of information about kernel.

And the kernel version requirement is one of the top FAQ from users when they want to choose a new OS or kernel.

Besides, some new features like RRO\ User Namespace\ cgroup v2 needs new kernels.

I try to summarize them in a page to make users clear when choosing a kernel version for their clusters.

Issue

xref kubernetes/kubernetes#116799

What's more?

This page did not include those bug-fixes or version compatibility improvement that are related to kernel versions like:

faster mount detection for linux kernel 5.10+ using openat2 speeding up pod churn rates. On Kernel versions less 5.10, it will fallback to using the original way of detecting mount points i.e by parsing /proc/mounts. Improved mount detection using openat2 for kernel 5.10+ kubernetes#109217
The sysctl net.ipv4.vs.conn_reuse_mode is left as-is for kernels >=5.9 rather that explicitly set to 1 Don't set sysctl net.ipv4.vs.conn_reuse_mode for kernels >=5.9 kubernetes#102122

- torvalds/linux@12ed824

pacoxu · 2024-08-05T10:56:42Z

content/en/docs/tasks/administer-cluster/sysctl-cluster.md

@@ -86,7 +86,7 @@ The following sysctls are supported in the _safe_ set:
 There are some exceptions to the set of safe sysctls:

 - The `net.*` sysctls are not allowed with host networking enabled.
- The `net.ipv4.tcp_syncookies` sysctl is not namespaced on Linux kernel version 4.4 or lower.
+- The `net.ipv4.tcp_syncookies` sysctl is not namespaced on Linux kernel version 4.5 or lower.


See torvalds/linux@12ed824 which is merged in 4.6.

netlify · 2024-08-05T11:03:32Z

✅ Pull request preview available for checking

Built without sensitive environment variables

Name	Link
🔨 Latest commit	`af8df3a`
🔍 Latest deploy log	https://app.netlify.com/sites/kubernetes-io-main-staging/deploys/66cc1a2ff05cac0008de7e54
😎 Deploy Preview	https://deploy-preview-47363--kubernetes-io-main-staging.netlify.app
📱 Preview on mobile	Toggle QR Code... Use your smartphone camera to open QR code link.

To edit notification comments on pull requests, go to your Netlify site configuration.

sftim · 2024-08-05T11:30:02Z

/retitle Document kernel version requirements for Linux

/sig architecture node

sftim

Thanks

Let's make it clear this page is about Linux (and not Windows, which also has a kernel).

content/en/docs/reference/node/kernel-version-requirements.md

sftim · 2024-08-05T11:35:14Z

content/en/docs/reference/node/kernel-version-requirements.md

+[`nftables` proxy mode](/docs/reference/networking/virtual-ips/#proxy-mode-nftables) is introduced in v1.29.
+The (alpha) nftables mode of kube-proxy now requires version 1.0.1 or later
+of the nft command-line, and kernel 5.13 or later. (For testing/development
+purposes, you can use older kernels, as far back as 5.4, if you set the
+`nftables.skipKernelVersionCheck` option in the kube-proxy config, but this is not
+recommended in production since it may cause problems with other nftables
+users on the system.


This will become stale with the v1.31 release. Can we write it to be more neutral as to whether nftables support is alpha / beta / stable?

Removed the alpha description here and only mentioned that the kernel version requirement.

content/en/docs/reference/node/kernel-version-requirements.md

SergeyKanzhelev · 2024-08-06T05:18:52Z

content/en/docs/reference/node/kernel-version-requirements.md

+
+Many features rely on specific kernel functionalities and have minimum kernel version requirements.
+
+## Pod sysctls {#requirements-pod-sysctl}


Would be great to have comment in this page pointing back to the constants in kubelet for each of the mentioned limitations. This way maintaining this page will be easier long term



19a4a01 Added some code reference.

I don't think we need to customize the anchor ID for the subsection line.

content/en/docs/reference/node/kernel-version-requirements.md

sftim

/hold

We can't / wouldn't make a statement about v1.31 prior to its release (see https://kubernetes.io/docs/contribute/style/style-guide/#avoid-statements-about-the-future - there are no obvious grounds for an exception).

This PR could target v1.31, or we can omit the detail about Kubernetes specifically recommending cgroup v2 (moving cgroup v1 support to maintenance only).

content/en/docs/reference/node/kernel-version-requirements.md

rphillips · 2024-08-06T17:41:06Z

The Kubelet and other low level components need to test the running the kernel if a feature is enabled. Can you add a blurb to this document? Kernel Vendors (RHEL, Debian, etc) often backport features and so going by kernel version number is not adequate for certain OS distributions.

pacoxu · 2024-08-07T02:40:45Z

@sftim yes, this may hold until 1.31 release.

The Kubelet and other low level components need to test the running the kernel if a feature is enabled. Can you add a blurb to this document? Kernel Vendors (RHEL, Debian, etc) often backport features and so going by kernel version number is not adequate for certain OS distributions.

Added. Not sure if this is proper.

However, relying solely on kernel version numbers may not be sufficient
for certain operating system distributions,
as kernel vendors such as RHEL, Ubuntu and SUSE often backport features to older kernels.

SergeyKanzhelev

lgtm, there is one link change recommendation that would be nice to apply

SergeyKanzhelev

/lgtm

k8s-ci-robot · 2024-08-20T05:56:10Z

LGTM label has been added.

Git tree hash: 1fce3e5070dcf18c9ef89ced1df9ff1f13fbe241

content/en/docs/reference/node/kernel-version-requirements.md

tengqm · 2024-08-16T03:18:00Z

content/en/docs/reference/node/kernel-version-requirements.md

+
+Many features rely on specific kernel functionalities and have minimum kernel version requirements.
+
+## Pod sysctls {#requirements-pod-sysctl}


I don't think we need to customize the anchor ID for the subsection line.

content/en/docs/reference/node/kernel-version-requirements.md

tengqm · 2024-08-26T07:50:11Z

/lgtm

k8s-ci-robot · 2024-08-26T07:50:18Z

LGTM label has been added.

Git tree hash: ea31a50cbf632d377bc5f8682c83b323e044be4e

sftim · 2024-08-27T15:51:24Z

v1.31 has been released
/hold cancel

sftim

Let's ship this, even with the tiny snag.

/approve

sftim · 2024-08-27T15:52:39Z

content/en/docs/reference/node/kernel-version-requirements.md

+Many features rely on specific kernel functionalities and have minimum kernel version requirements.
+However, relying solely on kernel version numbers may not be sufficient
+for certain operating system distributions,
+as maintainers for distributions such as RHEL, Ubuntu and SUSE often backport selected features


@pacoxu we should list these vendors in alphabetical order. Willing to send in a follow up PR?

k8s-ci-robot · 2024-08-27T15:53:09Z

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: SergeyKanzhelev, sftim

The full list of commands accepted by this bot can be found here.

The pull request process is described here

Needs approval from an approver in each of these files:

~~content/en/docs/OWNERS~~ [sftim]

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment

sysctl is moved to namespaced in 4.6

afc8fd9

- torvalds/linux@12ed824

k8s-ci-robot requested review from mengjiao-liu and sttts August 5, 2024 10:56

k8s-ci-robot added language/en Issues or PRs related to English language cncf-cla: yes Indicates the PR's author has signed the CNCF CLA. size/M Denotes a PR that changes 30-99 lines, ignoring generated files. labels Aug 5, 2024

pacoxu commented Aug 5, 2024

View reviewed changes

k8s-ci-robot added sig/architecture Categorizes an issue or PR as relevant to SIG Architecture. sig/node Categorizes an issue or PR as relevant to SIG Node. labels Aug 5, 2024

k8s-ci-robot changed the title ~~Kernel version requirements~~ Document kernel version requirements for Linux Aug 5, 2024

sftim reviewed Aug 5, 2024

View reviewed changes

pacoxu force-pushed the kernel-version-requirements branch from cd6a79a to 26ac83b Compare August 6, 2024 02:08

SergeyKanzhelev reviewed Aug 6, 2024

View reviewed changes

content/en/docs/reference/node/kernel-version-requirements.md Outdated Show resolved Hide resolved

SergeyKanzhelev reviewed Aug 6, 2024

View reviewed changes

add a page for kernel version requirements

e9ad39d

pacoxu force-pushed the kernel-version-requirements branch from 26ac83b to 19a4a01 Compare August 6, 2024 06:38

sftim reviewed Aug 6, 2024

View reviewed changes

content/en/docs/reference/node/kernel-version-requirements.md Outdated Show resolved Hide resolved

sftim reviewed Aug 6, 2024

View reviewed changes

content/en/docs/reference/node/kernel-version-requirements.md Outdated Show resolved Hide resolved

content/en/docs/reference/node/kernel-version-requirements.md Outdated Show resolved Hide resolved

content/en/docs/reference/node/kernel-version-requirements.md Outdated Show resolved Hide resolved

k8s-ci-robot added the do-not-merge/hold Indicates that a PR should not merge because someone has issued a /hold command. label Aug 6, 2024

pacoxu force-pushed the kernel-version-requirements branch 2 times, most recently from 43b85fe to 55ff16c Compare August 7, 2024 02:40

SergeyKanzhelev reviewed Aug 15, 2024

View reviewed changes

SergeyKanzhelev approved these changes Aug 20, 2024

View reviewed changes

k8s-ci-robot assigned SergeyKanzhelev Aug 20, 2024

k8s-ci-robot added the lgtm "Looks good to me", indicates that a PR is ready to be merged. label Aug 20, 2024

tengqm reviewed Aug 25, 2024

View reviewed changes

k8s-ci-robot requested a review from danwinship August 26, 2024 05:24

pacoxu force-pushed the kernel-version-requirements branch from ee8b09d to cb3a8de Compare August 26, 2024 05:30

k8s-ci-robot removed the lgtm "Looks good to me", indicates that a PR is ready to be merged. label Aug 26, 2024

k8s-ci-robot requested a review from SergeyKanzhelev August 26, 2024 05:30

tengqm reviewed Aug 26, 2024

View reviewed changes

content/en/docs/reference/node/kernel-version-requirements.md Outdated Show resolved Hide resolved

add code reference for kernel version check

af8df3a

pacoxu force-pushed the kernel-version-requirements branch from cb3a8de to af8df3a Compare August 26, 2024 06:01

k8s-ci-robot assigned tengqm Aug 26, 2024

k8s-ci-robot added the lgtm "Looks good to me", indicates that a PR is ready to be merged. label Aug 26, 2024

k8s-ci-robot removed the do-not-merge/hold Indicates that a PR should not merge because someone has issued a /hold command. label Aug 27, 2024

sftim reviewed Aug 27, 2024

View reviewed changes

k8s-ci-robot added the approved Indicates a PR has been approved by an approver from all required OWNERS files. label Aug 27, 2024

k8s-ci-robot merged commit 4f41986 into kubernetes:main Aug 27, 2024
6 checks passed

Provide feedback

Saved searches

Use saved searches to filter your results more quickly

Document kernel version requirements for Linux #47363

Document kernel version requirements for Linux #47363

pacoxu commented Aug 5, 2024

pacoxu Aug 5, 2024

netlify bot commented Aug 5, 2024 •

edited

Loading

sftim commented Aug 5, 2024

sftim left a comment

sftim Aug 5, 2024

pacoxu Aug 6, 2024 •

edited

Loading

SergeyKanzhelev Aug 6, 2024

pacoxu Aug 6, 2024

tengqm Aug 16, 2024

sftim left a comment

rphillips commented Aug 6, 2024

pacoxu commented Aug 7, 2024

SergeyKanzhelev left a comment

SergeyKanzhelev left a comment

k8s-ci-robot commented Aug 20, 2024

tengqm Aug 16, 2024

tengqm commented Aug 26, 2024

k8s-ci-robot commented Aug 26, 2024

sftim commented Aug 27, 2024

sftim left a comment

sftim Aug 27, 2024

k8s-ci-robot commented Aug 27, 2024


		Many features rely on specific kernel functionalities and have minimum kernel version requirements.

		## Pod sysctls {#requirements-pod-sysctl}

Document kernel version requirements for Linux #47363

Document kernel version requirements for Linux #47363

Conversation

pacoxu commented Aug 5, 2024

Description

Issue

What's more?

pacoxu Aug 5, 2024

Choose a reason for hiding this comment

netlify bot commented Aug 5, 2024 • edited Loading

✅ Pull request preview available for checking

sftim commented Aug 5, 2024

sftim left a comment

Choose a reason for hiding this comment

sftim Aug 5, 2024

Choose a reason for hiding this comment

pacoxu Aug 6, 2024 • edited Loading

Choose a reason for hiding this comment

SergeyKanzhelev Aug 6, 2024

Choose a reason for hiding this comment

pacoxu Aug 6, 2024

Choose a reason for hiding this comment

tengqm Aug 16, 2024

Choose a reason for hiding this comment

sftim left a comment

Choose a reason for hiding this comment

rphillips commented Aug 6, 2024

pacoxu commented Aug 7, 2024

SergeyKanzhelev left a comment

Choose a reason for hiding this comment

SergeyKanzhelev left a comment

Choose a reason for hiding this comment

k8s-ci-robot commented Aug 20, 2024

tengqm Aug 16, 2024

Choose a reason for hiding this comment

tengqm commented Aug 26, 2024

k8s-ci-robot commented Aug 26, 2024

sftim commented Aug 27, 2024

sftim left a comment

Choose a reason for hiding this comment

sftim Aug 27, 2024

Choose a reason for hiding this comment

k8s-ci-robot commented Aug 27, 2024

netlify bot commented Aug 5, 2024 •

edited

Loading

pacoxu Aug 6, 2024 •

edited

Loading