Change:
This is a Feature Request I want to ask a new documentation section under describing various aspects of moving away from Dockershim to other runtimes. One document I am working with is: There are more sub-topics will be there. Is there any concerns with creating this section? It will be relatively short-lived, but definitely beneficial for k8s users. What would you like to be Section under regarding migrating away from Dockershim. Why is this needed Since this announcement: there are a still things needed clarification which raise questions. /sig node
A Task page is the right kind of content to add. Are you considering adding a section inside ? I would add that rather than one inside - the deeper structure can be OK so long as we make sure there are lots of links to it. When that content disappears, where will we redirect to? I assume we'd want to add redirects
what do you think of this: Is it the right structure?
Hi . I started to read through PR . The location under tasks seems fine, though, you could create a new sub-directory () under tasks so that the content is not lost in the section. The new section could be titled something like: "Manage Dockershim migration" or "Migrate from Dockershim". What do you think about creating an outline (in this issue) of the sub-tasks to include in this section?
this was my original idea of a location, but suggested to place it under the administer section. looking at the content, should it be moved to it's own section? Some topics like monitoring agents is more of an application management than administering of a cluster.
My concerns from before stand, but they're not hard don't-do-this objections.
/triage accepted anyway
Hi . I'll spend some time to read the PR and doc. After a quick read, I think it probably make sense to separate the content from the tasks. Again, it is a good idea to write an outline of the content. This may help to determine where to put the content once the content is created.
Hope this is okay: /assign

Discussion:
<ins> --- title: "Migrating from dockershim" weight: 10 content_type: task --- <!-- overview --> This section presents information you need to know when migrating from dockershim to other container runtimes. Since the announcement of [dockershim deprecation](/blog/2020/12/08/kubernetes-1-20-release-announcement/#dockershim-deprecation) in Kubernetes 1.20, there were questions on how this will affect various workloads and Kubernetes installations. You can find this blog post useful to understand the problem better: [Dockershim Deprecation FAQ](/blog/2020/12/02/dockershim-faq/) It is recommended to migrate from dockershim to alternative container runtimes. Check out [container runtimes](/docs/setup/production-environment/container-runtimes/) section to know your options. Make sure to [report issues](https://github.com/kubernetes/kubernetes/issues) you encountered with the migration. So the issue can be fixed in a timely manner and your cluster would be ready for dockershim removal. </ins>

<ins> --- title: Check whether Dockershim deprecation affects you content_type: task reviewers: - SergeyKanzhelev weight: 20 --- <!-- overview --> The `dockershim` component of Kubernetes allows to use Docker as a Kubernetes's {{< glossary_tooltip text="container runtime" term_id="container-runtime" >}}. Kubernetes' built-in `dockershim` component was deprecated in release v1.20. This page explains how your cluster could be using Docker as a container runtime, provides details on the role that `dockershim` plays when in use, and shows steps you can take to check whether any workloads could be affected by `dockershim` deprecation. ## Finding if your app has a dependencies on Docker {#find-docker-dependencies} If you are using Docker for building your application containers, you can still run these containers on any container runtime. This use of Docker does not count as a dependency on Docker as a container runtime. When alternative container runtime is used, executing Docker commands may either not work or yield unexpected output. This is how you can find whether you have a dependency on Docker: 1. Make sure no privileged Pods execute Docker commands. 2. Check that scripts and apps running on nodes outside of Kubernetes infrastructure do not execute Docker commands. It might be: - SSH to nodes to troubleshoot; - Node startup scripts; - Monitoring and security agents installed on nodes directly. 3. Third-party tools that perform above mentioned privileged operations. See [Migrating telemetry and security agents from dockershim](/docs/tasks/administer-cluster/migrating-from-dockershim/migrating-telemetry-and-security-agents) for more information. 4. Make sure there is no indirect dependencies on dockershim behavior. This is an edge case and unlikely to affect your application. Some tooling may be configured to react to Docker-specific behaviors, for example, raise alert on specific metrics or search for a specific log message as part of troubleshooting instructions. If you have such tooling configured, test the behavior on test cluster before migration. ## Dependency on Docker explained {#role-of-dockershim} A [container runtime](/docs/concepts/containers/#container-runtimes) is software that can execute the containers that make up a Kubernetes pod. Kubernetes is responsible for orchestration and scheduling of Pods; on each node, the {{< glossary_tooltip text="kubelet" term_id="kubelet" >}} uses the container runtime interface as an abstraction so that you can use any compatible container runtime. In its earliest releases, Kubernetes offered compatibility with just one container runtime: Docker. Later in the Kubernetes project's history, cluster operators wanted to adopt additional container runtimes. The CRI was designed to allow this kind of flexibility - and the kubelet began supporting CRI. However, because Docker existed before the CRI specification was invented, the Kubernetes project created an adapter component, `dockershim`. The dockershim adapter allows the kubelet to interact with Docker as if Docker were a CRI compatible runtime. You can read about it in [Kubernetes Containerd integration goes GA](/blog/2018/05/24/kubernetes-containerd-integration-goes-ga/) blog post. ![Dockershim vs. CRI with Containerd](/images/blog/2018-05-24-kubernetes-containerd-integration-goes-ga/cri-containerd.png) Switching to Containerd as a container runtime eliminates the middleman. All the same containers can be run by container runtimes like Containerd as before. But now, since containers schedule directly with the container runtime, they are not visible to Docker. So any Docker tooling or fancy UI you might have used before to check on these containers is no longer available. You cannot get container information using `docker ps` or `docker inspect` commands. As you cannot list containers, you cannot get logs, stop containers, or execute something inside container using `docker exec`. {{< note >}} If you're running workloads via Kubernetes, the best way to stop a container is through the Kubernetes API rather than directly through the container runtime (this advice applies for all container runtimes, not just Docker). {{< /note >}} You can still pull images or build them using `docker build` command. But images built or pulled by Docker would not be visible to container runtime and Kubernetes. They needed to be pushed to some registry to allow them to be used by Kubernetes. </ins>

<ins> --- title: Migrating telemetry and security agents from dockershim content_type: task reviewers: - SergeyKanzhelev weight: 70 --- <!-- overview --> With Kubernetes 1.20 dockershim was deprecated. From the [Dockershim Deprecation FAQ](/blog/2020/12/02/dockershim-faq/) you might already know that most apps do not have a direct dependency on runtime hosting containers. However, there are still a lot of telemetry and security agents that has a dependency on docker to collect containers metadata, logs and metrics. This document aggregates information on how to detect these dependencies and links on how to migrate these agents to use generic tools or alternative runtimes. ## Telemetry and security agents There are a few ways agents may run on Kubernetes cluster. Agents may run on nodes directly or as DaemonSets. ### Why do telemetry agents rely on Docker? Historically, Kubernetes was built on top of Docker. Kubernetes is managing networking and scheduling, Docker was placing and operating containers on a node. So you can get scheduling-related metadata like a pod name from Kubernetes and containers state information from Docker. Over time more runtimes were created to manage containers. Also there are projects and Kubernetes features that generalize container status information extraction across many runtimes. Some agents are tied specifically to the Docker tool. The agents may run commands like [`docker ps`](https://docs.docker.com/engine/reference/commandline/ps/) or [`docker top`](https://docs.docker.com/engine/reference/commandline/top/) to list containers and processes or [docker logs](https://docs.docker.com/engine/reference/commandline/logs/) to subscribe on docker logs. With the deprecating of Docker as a container runtime, these commands will not work any longer. ### Identify DaemonSets that depend on Docker {#identify-docker-dependency} If a pod wants to make calls to the `dockerd` running on the node, the pod must either: - mount the filesystem containing the Docker daemon's privileged socket, as a {{< glossary_tooltip text="volume" term_id="volume" >}}; or - mount the specific path of the Docker daemon's privileged socket directly, also as a volume. For example: on COS images, Docker exposes its Unix domain socket at `/var/run/docker.sock` This means that the pod spec will include a `hostPath` volume mount of `/var/run/docker.sock`. Here's a sample shell script to find Pods that have a mount directly mapping the Docker socket. This script outputs the namespace and name of the pod. You can remove the grep `/var/run/docker.sock` to review other mounts. ```bash kubectl get pods --all-namespaces  -o=jsonpath='{range .items[*]}{"n"}{.metadata.namespace}{":t"}{.metadata.name}{":t"}{range .spec.volumes[*]}{.hostPath.path}{", "}{end}{end}'  | sort  | grep '/var/run/docker.sock' ``` {{< note >}} There are alternative ways for a pod to access Docker on the host. For instance, the parent directory `/var/run` may be mounted instead of the full path (like in [this example](https://gist.github.com/itaysk/7bc3e56d69c4d72a549286d98fd557dd)). The script above only detects the most common uses. {{< /note >}} ### Detecting Docker dependency from node agents In case your cluster nodes are customized and install additional security and telemetry agents on the node, make sure to check with the vendor of the agent whether it has dependency on Docker. ### Telemetry and security agent vendors We keep the work in progress version of migration instructions for various telemetry and security agent vendors in [Google doc](https://docs.google.com/document/d/1ZFi4uKit63ga5sxEiZblfb-c23lFhvy6RXVPikS8wf0/edit#). Please contact the vendor to get up to date instructions for migrating from dockershim. </ins>