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Update dockershim removal FAQ for v1.24 release

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Co-authored-by: Shannon Kularathna <ax3shannonkularathna@gmail.com>
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Tim Bannister
2022-04-23 11:52:06 +01:00
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@@ -7,31 +7,35 @@ slug: dockershim-faq
aliases: [ '/dockershim' ] aliases: [ '/dockershim' ]
--- ---
**This is an update to the original [Dockershim Deprecation FAQ](/blog/2020/12/02/dockershim-faq/) article, **This supersedes the original [Dockershim Deprecation FAQ](/blog/2020/12/02/dockershim-faq/) article,
published in late 2020.** published in late 2020.**
---
This document goes over some frequently asked questions regarding the This document goes over some frequently asked questions regarding the
deprecation and removal of _dockershim_, that was removal of _dockershim_ from Kubernetes. The removal was originally
[announced](/blog/2020/12/08/kubernetes-1-20-release-announcement/) [announced](/blog/2020/12/08/kubernetes-1-20-release-announcement/)
as a part of the Kubernetes v1.20 release. For more detail as a part of the Kubernetes v1.20 release. The Kubernetes
on what that means, check out the blog post [v1.24 release](/releases/#release-v1-24) actually removed the dockershim
from Kubernetes.
For more on what that means, check out the blog post
[Don't Panic: Kubernetes and Docker](/blog/2020/12/02/dont-panic-kubernetes-and-docker/). [Don't Panic: Kubernetes and Docker](/blog/2020/12/02/dont-panic-kubernetes-and-docker/).
Also, you can read [check whether dockershim removal affects you](/docs/tasks/administer-cluster/migrating-from-dockershim/check-if-dockershim-removal-affects-you/) To determine the impact that the removal of dockershim would have for you or your organization,
to determine how much impact the removal of dockershim would have for you you can read [Check whether dockershim removal affects you](/docs/tasks/administer-cluster/migrating-from-dockershim/check-if-dockershim-removal-affects-you/).
or for your organization.
As the Kubernetes 1.24 release has become imminent, we've been working hard to try to make this a smooth transition. In the months and days leading up to the Kubernetes 1.24 release, Kubernetes contributors worked hard to try to make this a smooth transition.
- We've written a blog post detailing our [commitment and next steps](/blog/2022/01/07/kubernetes-is-moving-on-from-dockershim/). - A blog post detailing our [commitment and next steps](/blog/2022/01/07/kubernetes-is-moving-on-from-dockershim/).
- We believe there are no major blockers to migration to [other container runtimes](/docs/setup/production-environment/container-runtimes/#container-runtimes). - Checking if there were major blockers to migration to [other container runtimes](/docs/setup/production-environment/container-runtimes/#container-runtimes).
- There is also a [Migrating from dockershim](/docs/tasks/administer-cluster/migrating-from-dockershim/) guide available. - Adding a [migrating from dockershim](/docs/tasks/administer-cluster/migrating-from-dockershim/) guide.
- We've also created a page to list - Creating a list of
[articles on dockershim removal and on using CRI-compatible runtimes](/docs/reference/node/topics-on-dockershim-and-cri-compatible-runtimes/). [articles on dockershim removal and on using CRI-compatible runtimes](/docs/reference/node/topics-on-dockershim-and-cri-compatible-runtimes/).
That list includes some of the already mentioned docs, and also covers selected external sources That list includes some of the already mentioned docs, and also covers selected external sources
(including vendor guides). (including vendor guides).
### Why is the dockershim being removed from Kubernetes? ### Why was the dockershim removed from Kubernetes?
Early versions of Kubernetes only worked with a specific container runtime: Early versions of Kubernetes only worked with a specific container runtime:
Docker Engine. Later, Kubernetes added support for working with other container runtimes. Docker Engine. Later, Kubernetes added support for working with other container runtimes.
@@ -49,36 +53,18 @@ In fact, maintaining dockershim had become a heavy burden on the Kubernetes main
Additionally, features that were largely incompatible with the dockershim, such Additionally, features that were largely incompatible with the dockershim, such
as cgroups v2 and user namespaces are being implemented in these newer CRI as cgroups v2 and user namespaces are being implemented in these newer CRI
runtimes. Removing support for the dockershim will allow further development in runtimes. Removing the dockershim from Kubernetes allows further development in those areas.
those areas.
[drkep]: https://github.com/kubernetes/enhancements/tree/master/keps/sig-node/2221-remove-dockershim [drkep]: https://github.com/kubernetes/enhancements/tree/master/keps/sig-node/2221-remove-dockershim
### Can I still use Docker Engine in Kubernetes 1.23? ### Are Docker and containers the same thing?
Yes, the only thing changed in 1.20 is a single warning log printed at [kubelet] Docker popularized the Linux containers pattern and has been instrumental in
startup if using Docker Engine as the runtime. You'll see this warning in all versions up to 1.23. The dockershim removal occurs in Kubernetes 1.24. developing the underlying technology, however containers in Linux have existed
for a long time. The container ecosystem has grown to be much broader than just
[kubelet]: /docs/reference/command-line-tools-reference/kubelet/ Docker. Standards like OCI and CRI have helped many tools grow and thrive in our
ecosystem, some replacing aspects of Docker while others enhance existing
### When will dockershim be removed? functionality.
Given the impact of this change, we are using an extended deprecation timeline.
Removal of dockershim is scheduled for Kubernetes v1.24, see [Dockershim Removal Kubernetes Enhancement Proposal][drkep].
The Kubernetes project will be working closely with vendors and other ecosystem groups to ensure
a smooth transition and will evaluate things as the situation evolves.
### Can I still use Docker Engine as my container runtime?
First off, if you use Docker on your own PC to develop or test containers: nothing changes.
You can still use Docker locally no matter what container runtime(s) you use for your
Kubernetes clusters. Containers make this kind of interoperability possible.
Mirantis and Docker have [committed][mirantis] to maintaining a replacement adapter for
Docker Engine, and to maintain that adapter even after the in-tree dockershim is removed
from Kubernetes. The replacement adapter is named [`cri-dockerd`](https://github.com/Mirantis/cri-dockerd).
[mirantis]: https://www.mirantis.com/blog/mirantis-to-take-over-support-of-kubernetes-dockershim-2/
### Will my existing container images still work? ### Will my existing container images still work?
@@ -90,14 +76,41 @@ All your existing images will still work exactly the same.
Yes. All CRI runtimes support the same pull secrets configuration used in Yes. All CRI runtimes support the same pull secrets configuration used in
Kubernetes, either via the PodSpec or ServiceAccount. Kubernetes, either via the PodSpec or ServiceAccount.
### Are Docker and containers the same thing? ### Can I still use Docker Engine in Kubernetes 1.23?
Docker popularized the Linux containers pattern and has been instrumental in Yes, the only thing changed in 1.20 is a single warning log printed at [kubelet]
developing the underlying technology, however containers in Linux have existed startup if using Docker Engine as the runtime. You'll see this warning in all versions up to 1.23. The dockershim removal occurred
for a long time. The container ecosystem has grown to be much broader than just in Kubernetes 1.24.
Docker. Standards like OCI and CRI have helped many tools grow and thrive in our
ecosystem, some replacing aspects of Docker while others enhance existing If you're running Kubernetes v1.24 or later, see [Can I still use Docker Engine as my container runtime?](#can-i-still-use-docker-engine-as-my-container-runtime).
functionality. (Remember, you can switch away from the dockershim if you're using any supported Kubernetes release; from release v1.24, you
**must** switch as Kubernetes no longer incluides the dockershim).
[kubelet]: /docs/reference/command-line-tools-reference/kubelet/
### Which CRI implementation should I use?
That’s a complex question and it depends on a lot of factors. If Docker Engine is
working for you, moving to containerd should be a relatively easy swap and
will have strictly better performance and less overhead. However, we encourage you
to explore all the options from the [CNCF landscape] in case another would be an
even better fit for your environment.
[CNCF landscape]: https://landscape.cncf.io/card-mode?category=container-runtime&grouping=category
#### Can I still use Docker Engine as my container runtime?
First off, if you use Docker on your own PC to develop or test containers: nothing changes.
You can still use Docker locally no matter what container runtime(s) you use for your
Kubernetes clusters. Containers make this kind of interoperability possible.
Mirantis and Docker have [committed][mirantis] to maintaining a replacement adapter for
Docker Engine, and to maintain that adapter even after the in-tree dockershim is removed
from Kubernetes. The replacement adapter is named [`cri-dockerd`](https://github.com/Mirantis/cri-dockerd).
You can install `cri-dockerd` and use it to connect the kubelet to Docker Engine. Read [Migrate Docker Engine nodes from dockershim to cri-dockerd](/docs/tasks/administer-cluster/migrating-from-dockershim/migrate-dockershim-dockerd/) to learn more.
[mirantis]: https://www.mirantis.com/blog/mirantis-to-take-over-support-of-kubernetes-dockershim-2/
### Are there examples of folks using other runtimes in production today? ### Are there examples of folks using other runtimes in production today?
@@ -135,16 +148,6 @@ provide an end-to-end standard for managing containers.
[runc]: https://github.com/opencontainers/runc [runc]: https://github.com/opencontainers/runc
[containerd]: https://containerd.io/ [containerd]: https://containerd.io/
### Which CRI implementation should I use?
That’s a complex question and it depends on a lot of factors. If Docker is
working for you, moving to containerd should be a relatively easy swap and
will have strictly better performance and less overhead. However, we encourage you
to explore all the options from the [CNCF landscape] in case another would be an
even better fit for your environment.
[CNCF landscape]: https://landscape.cncf.io/card-mode?category=container-runtime&grouping=category
### What should I look out for when changing CRI implementations? ### What should I look out for when changing CRI implementations?
While the underlying containerization code is the same between Docker and most While the underlying containerization code is the same between Docker and most
@@ -153,24 +156,25 @@ common things to consider when migrating are:
- Logging configuration - Logging configuration
- Runtime resource limitations - Runtime resource limitations
- Node provisioning scripts that call docker or use docker via it's control socket - Node provisioning scripts that call docker or use Docker Engine via its control socket
- Kubectl plugins that require docker CLI or the control socket - Plugins for `kubectl` that require the `docker` CLI or the Docker Engine control socket
- Tools from the Kubernetes project that require direct access to Docker Engine - Tools from the Kubernetes project that require direct access to Docker Engine
(for example: the deprecated `kube-imagepuller` tool) (for example: the deprecated `kube-imagepuller` tool)
- Configuration of functionality like `registry-mirrors` and insecure registries - Configuration of functionality like `registry-mirrors` and insecure registries
- Other support scripts or daemons that expect Docker Engine to be available and are run - Other support scripts or daemons that expect Docker Engine to be available and are run
outside of Kubernetes (for example, monitoring or security agents) outside of Kubernetes (for example, monitoring or security agents)
- GPUs or special hardware and how they integrate with your runtime and Kubernetes - GPUs or special hardware and how they integrate with your runtime and Kubernetes
If you use Kubernetes resource requests/limits or file-based log collection If you use Kubernetes resource requests/limits or file-based log collection
DaemonSets then they will continue to work the same, but if you’ve customized DaemonSets then they will continue to work the same, but if you've customized
your `dockerd` configuration, you’ll need to adapt that for your new container your `dockerd` configuration, you’ll need to adapt that for your new container
runtime where possible. runtime where possible.
Another thing to look out for is anything expecting to run for system maintenance Another thing to look out for is anything expecting to run for system maintenance
or nested inside a container when building images will no longer work. For the or nested inside a container when building images will no longer work. For the
former, you can use the [`crictl`][cr] tool as a drop-in replacement (see [mapping from docker cli to crictl](https://kubernetes.io/docs/tasks/debug-application-cluster/crictl/#mapping-from-docker-cli-to-crictl)) and for the former, you can use the [`crictl`][cr] tool as a drop-in replacement (see
latter you can use newer container build options like [img], [buildah], [mapping from docker cli to crictl](https://kubernetes.io/docs/tasks/debug-application-cluster/crictl/#mapping-from-docker-cli-to-crictl))
and for the latter you can use newer container build options like [img], [buildah],
[kaniko], or [buildkit-cli-for-kubectl] that don’t require Docker. [kaniko], or [buildkit-cli-for-kubectl] that don’t require Docker.
[cr]: https://github.com/kubernetes-sigs/cri-tools [cr]: https://github.com/kubernetes-sigs/cri-tools
@@ -204,7 +208,7 @@ discussion of the changes.
[dep]: https://dev.to/inductor/wait-docker-is-deprecated-in-kubernetes-now-what-do-i-do-e4m [dep]: https://dev.to/inductor/wait-docker-is-deprecated-in-kubernetes-now-what-do-i-do-e4m
### Is there any tooling that can help me find dockershim in use ### Is there any tooling that can help me find dockershim in use?
Yes! The [Detector for Docker Socket (DDS)][dds] is a kubectl plugin that you can Yes! The [Detector for Docker Socket (DDS)][dds] is a kubectl plugin that you can
install and then use to check your cluster. DDS can detect if active Kubernetes workloads install and then use to check your cluster. DDS can detect if active Kubernetes workloads