Add sysctl support

[sttts]

Description

This feature aims at extending the current pod specification with support
for namespaced kernel parameters (sysctls) set for each pod.

Scope of work planned for v1.11

• graduate to beta

Progress Tracker

• Before Alpha
  • Design Approval
    • Design Proposal: Add sysctl proposal kubernetes#26057
    • Initial API review (if API).
      • cc @kubernetes/api
    • Identify shepherd (your SIG lead and/or kubernetes-pm@googlegroups.com will be able to help you). My Shepherd is: @vishh
    • Identify secondary/backup contact point @derekwaynecarr
  • Write (code done + tests done + docs done, ready to be merged) then get them merged. Add sysctl support kubernetes#27180
    • Code needs to be disabled by default. Verified by code OWNERS
    • Minimal testing
    • Minimal docs: Add docs/admin/sysctls.md website#1126
      • cc @kubernetes/docs on docs PR
      • cc @kubernetes/feature-reviewers on this issue to get approval before checking this off
      • New apis: Glossary Section Item in the docs repo: kubernetes/kubernetes.github.io
    • Update release notes
• Before Beta
  • Testing is sufficient for beta
  • User docs with tutorials
    • Updated walkthrough / tutorial in the docs repo: kubernetes/kubernetes.github.io
    • cc @kubernetes/docs on docs: Promote sysctls to Beta website#8804
    • cc @kubernetes/feature-reviewers on this issue to get approval before checking this off
  • Thorough API review
    • cc @kubernetes/api
• Before Stable
  • docs/proposals/foo.md moved to docs/design/foo.md
    • cc @kubernetes/feature-reviewers on this issue to get approval before checking this off
  • Soak, load testing
  • detailed user docs and examples
    • cc @kubernetes/docs
    • cc @kubernetes/feature-reviewers on this issue to get approval before checking this off

FEATURE_STATUS is used for feature tracking and to be updated by @kubernetes/feature-reviewers.
FEATURE_STATUS: IN_DEVELOPMENT

More advice:

Design

• Once you get LGTM from a @kubernetes/feature-reviewers member, you can check this checkbox, and the reviewer will apply the "design-complete" label.

Coding

• Use as many PRs as you need. Write tests in the same or different PRs, as is convenient for you.
• As each PR is merged, add a comment to this issue referencing the PRs. Code goes in the http://github.com/kubernetes/kubernetes repository,
  and sometimes http://github.com/kubernetes/contrib, or other repos.
• When you are done with the code, apply the "code-complete" label.
• When the feature has user docs, please add a comment mentioning @kubernetes/feature-reviewers and they will
  check that the code matches the proposed feature and design, and that everything is done, and that there is adequate
  testing. They won't do detailed code review: that already happened when your PRs were reviewed.
  When that is done, you can check this box and the reviewer will apply the "code-complete" label.

Docs

• Write user docs and get them merged in.
• User docs go into http://github.com/kubernetes/kubernetes.github.io.
• When the feature has user docs, please add a comment mentioning @kubernetes/docs.
• When you get LGTM, you can check this checkbox, and the reviewer will apply the "docs-complete" label.

[sttts]

@kubernetes/docs here are the sysctl docs: kubernetes/website#1126

[sttts]

/cc @kubernetes/feature-reviewers

[fejta-bot]

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[sttts]

There are a number of people using sysctls now. I have not heard any issues with them.

I suggest to promote the current API (transformed to native fields in the PSP and on pods) to beta for 1.11.

@jeremyeder @vishh @derekwaynecarr @php-coder

@kubernetes/sig-node-api-reviews