Add 'checkpoint' command to kubectl

[adrianreber]

What type of PR is this?

/kind feature

What this PR does / why we need it:

Kubernetes 1.25 introduced the possibility to checkpoint a container.

For details please see the KEP 2008 Forensic Container Checkpointing kubernetes/enhancements#2008

The initial implementation only provided a kubelet API endpoint to trigger a checkpoint. The main reason for not extending it to the API server and kubectl was that checkpointing is a completely new concept.

Although the result of the checkpointing, the checkpoint archive, is only accessible by root it is important to remember that it contains all memory pages and thus all possible passwords, private keys and random numbers. With the checkpoint archive being only accessible by root it does not directly make it easier to access this potentially confidential information as root would be able to retrieve that information anyway.

Now, at least three Kubernetes releases later, we have not heard any negative feedback about the checkpoint archive and its data. There were, however, many questions to be able to create a checkpoint via kubectl and not just via the kubelet API endpoint.

This commit adds 'checkpoint' support to kubectl. The 'checkpoint' command is heavily influenced by the code of the 'exec' and 'logs' command. The checkpoint command is only available behind the 'alpha' sub-command as the "Forensic Container Checkpointing" KEP is still marked as Alpha.

Example output:

 $ kubectl alpha checkpoint test-pod-1 -c container-2
 Node:                  127.0.0.1/127.0.0.1
 Namespace:             default
 Pod:                   test-pod-1
 Container:             container-2
 Checkpoint Archive:    /var/lib/kubelet/checkpoints/checkpoint-archive.tar

The tests are implemented that they handle a CRI implementation with and without a implementation of the CRI RPC call 'ContainerCheckpoint'.

Which issue(s) this PR fixes:

Special notes for your reviewer:

Does this PR introduce a user-facing change?

Added `checkpoint` command to kubectl.

Additional documentation e.g., KEPs (Kubernetes Enhancement Proposals), usage docs, etc.:

- [KEP]: https://github.com/kubernetes/enhancements/issues/2008

[k8s-ci-robot]

Hi @adrianreber. Thanks for your PR.

I'm waiting for a kubernetes member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

Once the patch is verified, the new status will be reflected by the ok-to-test label.

I understand the commands that are listed here.

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 kubernetes/test-infra repository.

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: adrianreber
Once this PR has been reviewed and has the lgtm label, please assign deads2k for approval. For more information see the Kubernetes Code Review Process.

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

Needs approval from an approver in each of these files:

• api/OWNERS
• pkg/apis/OWNERS
• pkg/generated/openapi/OWNERS
• pkg/registry/OWNERS
• staging/src/k8s.io/api/OWNERS
• staging/src/k8s.io/kubectl/OWNERS
• test/e2e/kubectl/OWNERS

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

[adrianreber]

@mikebrow PTAL

[jiahuif]

/assign @mikebrow
/triage accepted

[k8s-triage-robot]

The Kubernetes project currently lacks enough active contributors to adequately respond to all issues and PRs.

This bot triages PRs according to the following rules:

• After 90d of inactivity, lifecycle/stale is applied
• After 30d of inactivity since lifecycle/stale was applied, lifecycle/rotten is applied
• After 30d of inactivity since lifecycle/rotten was applied, the PR is closed

You can:

• Reopen this PR with /reopen
• Mark this PR as fresh with /remove-lifecycle rotten
• Offer to help out with Issue Triage

Please send feedback to sig-contributor-experience at kubernetes/community.

/close

[k8s-ci-robot]

@k8s-triage-robot: Closed this PR.

In response to this:

The Kubernetes project currently lacks enough active contributors to adequately respond to all issues and PRs.

This bot triages PRs according to the following rules:

• After 90d of inactivity, lifecycle/stale is applied
• After 30d of inactivity since lifecycle/stale was applied, lifecycle/rotten is applied
• After 30d of inactivity since lifecycle/rotten was applied, the PR is closed

You can:

• Reopen this PR with /reopen
• Mark this PR as fresh with /remove-lifecycle rotten
• Offer to help out with Issue Triage

Please send feedback to sig-contributor-experience at kubernetes/community.

/close

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 kubernetes/test-infra repository.

[mochizuki875]

Hi, I'm watching this issue and having high hopes for this feature.
I think it would be convenient to allow k8s user to checkpoint the specific container using kubectl.
Will this PR not be restarted?

[adrianreber]

/remove-lifecycle rotten

[adrianreber]

/reopen

[k8s-ci-robot]

@adrianreber: Reopened this PR.

In response to this:

/reopen

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 kubernetes/test-infra repository.

[bart0sh]

@adrianreber please, rebase the PR, thanks!

[k8s-triage-robot]

This PR may require API review.

If so, when the changes are ready, complete the pre-review checklist and request an API review.

Status of requested reviews is tracked in the API Review project.