Kubelet refuses to start, complaining that the CRI runtime API is not implemented for my endpoint

The practical route, since the distribution package is the problem:

1. Add the container runtime's own repository rather than using the distribution's package. Every major runtime publishes one, and it carries current versions.
2. Install a version that implements the current CRI, then confirm with the runtime's own version command before restarting anything.
3. Check the configuration file was regenerated after the upgrade. An old config file with an upgraded binary is the next failure you will hit, and it produces a different but equally opaque error.
4. Confirm the cgroup driver matches what the kubelet expects. Mismatched cgroup drivers are the classic follow-on problem on a fresh node and produce pods that start and then behave strangely under memory pressure.

Step 4 is worth doing proactively. It is the single most common reason a node comes up healthy and then misbehaves a week later.

This is a genuine version compatibility break rather than a misconfiguration, and knowing that saves a lot of wasted effort.

Kubernetes removed support for the older container runtime interface version at a specific release. From that release onward the kubelet speaks only the current API version. A container runtime that is older than that break implements only the previous one, so the two cannot talk at all — hence a failure at validation rather than a partial degradation.

So the mismatch is: your kubelet is newer than your container runtime. The fix is to upgrade the runtime to a version that implements the current API, not to change any kubelet setting.

The reason this catches people on a fresh node is that distribution repositories often carry an older runtime than the Kubernetes packages you added from a separate repository. Two package sources, two release cadences, and nothing warns you they have drifted apart.

Diagnostic worth knowing for this family of errors: the runtime's own command line client can query the CRI endpoint directly and report the version it serves.

Running that against the socket the kubelet is configured to use answers the question in one step — you see which API versions the endpoint actually offers, rather than inferring it from a failure. It also confirms you have the right socket path, which is the other half of this error's population.

The general lesson for anyone building nodes: pin the versions of the runtime and the Kubernetes components together, and treat them as one unit.

Kubernetes publishes a supported version skew for each release. Installing the kubelet from one repository and the runtime from another, both floating on latest, guarantees you will eventually meet a break like this one — usually during an unattended upgrade, at night, on a node that then fails to rejoin.

Hold the packages at chosen versions and upgrade them deliberately as a set. It is more work per upgrade and dramatically less work per incident.