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Merge pull request #28312 from antoinep92/patch-1 

Document recovery from broken kubelet certificate
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Kubernetes Prow Robot 2021-06-14 22:08:00 -07:00 committed by GitHub
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19
content/en/docs/setup/production-environment/tools/kubeadm/troubleshooting-kubeadm.md
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@ -220,6 +220,25 @@ Unable to connect to the server: x509: certificate signed by unknown authority (
sudo chown $(id -u):$(id -g) $HOME/.kube/config sudo chown $(id -u):$(id -g) $HOME/.kube/config
``` ```
## Kubelet client certificate rotation fails {#kubelet-client-cert}
By default, kubeadm configures a kubelet with automatic rotation of client certificates by using the `/var/lib/kubelet/pki/kubelet-client-current.pem` symlink specified in `/etc/kubernetes/kubelet.conf`.
If this rotation process fails you might see errors such as `x509: certificate has expired or is not yet valid`
in kube-apserver logs. To fix the issue you must follow these steps:
1. Backup and delete `/etc/kubernetes/kubelet.conf` and `/var/lib/kubelet/pki/kubelet-client*` from the failed node.
1. From a working control plane node in the cluster that has `/etc/kubernetes/pki/ca.key` execute
`kubeadm kubeconfig user --org system:nodes --client-name system:node:$NODE > kubelet.conf`.
`$NODE` must be set to the name of the existing failed node in the cluster.
Modify the resulted `kubelet.conf` manually to adjust the cluster name and server endpoint,
or pass `kubeconfig user --config` (it accepts `InitConfiguration`). If your cluster does not have
the `ca.key` you must sign the embedded certificates in the `kubelet.conf` externally.
1. Copy this resulted `kubelet.conf` to `/etc/kubernetes/kubelet.conf` on the failed node.
1. Restart the kubelet (`systemctl restart kubelet`) on the failed node and wait for
`/var/lib/kubelet/pki/kubelet-client-current.pem` to be recreated.
1. Run `kubeadm init phase kubelet-finalize all` on the failed node. This will make the new
`kubelet.conf` file use `/var/lib/kubelet/pki/kubelet-client-current.pem` and will restart the kubelet.
1. Make sure the node becomes `Ready`.
## Default NIC When using flannel as the pod network in Vagrant ## Default NIC When using flannel as the pod network in Vagrant
The following error might indicate that something was wrong in the pod network: The following error might indicate that something was wrong in the pod network:

6
content/en/docs/tasks/administer-cluster/kubeadm/kubeadm-certs.md
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@ -85,7 +85,11 @@ Additionally, kubeadm informs the user if the certificate is externally managed;
{{< /warning >}} {{< /warning >}}
{{< note >}} {{< note >}}
`kubelet.conf` is not included in the list above because kubeadm configures kubelet for automatic certificate renewal. `kubelet.conf` is not included in the list above because kubeadm configures kubelet
for [automatic certificate renewal](/docs/tasks/tls/certificate-rotation/)
with rotatable certificates under `/var/lib/kubelet/pki`.
To repair an expired kubelet client certificate see
[Kubelet client certificate rotation fails](/docs/setup/production-environment/tools/kubeadm/troubleshooting-kubeadm/#kubelet-client-cert).
{{< /note >}} {{< /note >}}
{{< warning >}} {{< warning >}}