Restoring to a previous cluster state

Restoring to a previous cluster state

To restore the cluster to a previous state, you must have previously backed up etcd data by creating a snapshot. You will use this snapshot to restore the cluster state.

You can use a saved etcd backup to restore back to a previous cluster state. You use the etcd backup to restore a single control plane host. Then the etcd cluster Operator handles scaling to the remaining master hosts.

When you restore your cluster, you must use an etcd backup that was taken from the same z-stream release. For example, an OpenShift Container Platform 4.5.2 cluster must use an etcd backup that was taken from 4.5.2.

Prerequisites

Access to the cluster as a user with the cluster-admin role.
A healthy master host to use as the recovery host.
SSH access to master hosts.
A backup directory containing both the etcd snapshot and the resources for the static pods, which were from the same backup. The file names in the directory must be in the following formats: snapshot_<datetimestamp>.db and static_kuberesources_<datetimestamp>.tar.gz.

Procedure

Select a control plane host to use as the recovery host. This is the host that you will run the restore operation on.
establish SSH connectivity to each of the control plane nodes, including the recovery host.

The Kubernetes API server becomes inaccessible after the restore process starts, so you cannot access the control plane nodes. For this reason, it is recommended to establish SSH connectivity to each control plane host in a separate terminal.

If you do not complete this step, you will not be able to access the master hosts to complete the restore procedure, and you will be unable to recover your cluster from this state.
Copy the etcd backup directory to the recovery control plane host.

This procedure assumes that you copied the backup directory containing the etcd snapshot and the resources for the static pods to the /home/core/ directory of your recovery control plane host.
Stop the static pods on all other control plane nodes.

It is not required to manually stop the pods on the recovery host. The recovery script will stop the pods on the recovery host.
1. Access a control plane host that is not the recovery host.
2. Move the existing etcd pod file out of the kubelet manifest directory:
  [core@ip-10-0-154-194 ~]$ sudo mv /etc/kubernetes/manifests/etcd-pod.yaml /tmp
3. Verify that the etcd pods are stopped.
  [core@ip-10-0-154-194 ~]$ sudo crictl ps | grep etcd | grep -v operator
  The output of this command should be empty. If it is not empty, wait a few minutes and check again.
4. Move the existing Kubernetes API server pod file out of the kubelet manifest directory:
  [core@ip-10-0-154-194 ~]$ sudo mv /etc/kubernetes/manifests/kube-apiserver-pod.yaml /tmp
5. Verify that the Kubernetes API server pods are stopped.
  [core@ip-10-0-154-194 ~]$ sudo crictl ps | grep kube-apiserver | grep -v operator
  The output of this command should be empty. If it is not empty, wait a few minutes and check again.
6. Move the etcd data directory to a different location:
  [core@ip-10-0-154-194 ~]$ sudo mv /var/lib/etcd/ /tmp
7. Repeat this step on each of the other master hosts that is not the recovery host.
Access the recovery control plane host.
If the cluster-wide proxy is enabled, be sure that you have exported the NO_PROXY, HTTP_PROXY, and HTTPS_PROXY environment variables.

You can check whether the proxy is enabled by reviewing the output of oc get proxy cluster -o yaml. The proxy is enabled if the httpProxy, httpsProxy, and noProxy fields have values set.

Run the restore script on the recovery control plane host and pass in the path to the etcd backup directory:

[core@ip-10-0-143-125 ~]$ sudo -e /usr/local/bin/cluster-restore.sh /home/core/backup

example script output

...stopping kube-scheduler-pod.yaml
...stopping kube-controller-manager-pod.yaml
...stopping etcd-pod.yaml
...stopping kube-apiserver-pod.yaml
Waiting for container etcd to stop
.complete
Waiting for container etcdctl to stop
.............................complete
Waiting for container etcd-metrics to stop
complete
Waiting for container kube-controller-manager to stop
complete
Waiting for container kube-apiserver to stop
..........................................................................................complete
Waiting for container kube-scheduler to stop
complete
Moving etcd data-dir /var/lib/etcd/member to /var/lib/etcd-backup
starting restore-etcd static pod
starting kube-apiserver-pod.yaml
static-pod-resources/kube-apiserver-pod-7/kube-apiserver-pod.yaml
starting kube-controller-manager-pod.yaml
static-pod-resources/kube-controller-manager-pod-7/kube-controller-manager-pod.yaml
starting kube-scheduler-pod.yaml
static-pod-resources/kube-scheduler-pod-8/kube-scheduler-pod.yaml

Restart the kubelet service on all master hosts.
1. From the recovery host, run the following command:
  [core@ip-10-0-143-125 ~]$ sudo systemctl restart kubelet.service
2. Repeat this step on all other master hosts.

Verify that the single member control plane has started successfully.

From the recovery host, verify that the etcd container is running.

[core@ip-10-0-143-125 ~]$ sudo crictl ps | grep etcd | grep -v operator

example output

3ad41b7908e32       36f86e2eeaaffe662df0d21041eb22b8198e0e58abeeae8c743c3e6e977e8009                                                         About a minute ago   Running             etcd                                          0                   7c05f8af362f0

From the recovery host, verify that the etcd pod is running.

[core@ip-10-0-143-125 ~]$ oc get pods -n openshift-etcd | grep etcd

If you attempt to run oc login prior to running this command and receive the following error, wait a few moments for the authentication controllers to start and try again.

Unable to connect to the server: eOF

example output

NAMe                                             ReADY   STATUS      ReSTARTS   AGe
etcd-ip-10-0-143-125.ec2.internal                1/1     Running     1          2m47s

If the status is Pending, or the output lists more than one running etcd pod, wait a few minutes and check again.

Force etcd redeployment.

In a terminal that has access to the cluster as a cluster-admin user, run the following command:
```
$ oc patch etcd cluster -p='{"spec": {"forceRedeploymentReason": "recovery-'"$( date --rfc-3339=ns )"'"}}' --type=merge (1)
```
1 The forceRedeploymentReason value must be unique, which is why a timestamp is appended.

When the etcd cluster Operator performs a redeployment, the existing nodes are started with new pods similar to the initial bootstrap scale up.
Verify all nodes are updated to the latest revision.

In a terminal that has access to the cluster as a cluster-admin user, run the following command:
```
$ oc get etcd -o=jsonpath='{range .items[0].status.conditions[?(@.type=="NodeInstallerProgressing")]}{.reason}{"\n"}{.message}{"\n"}'
```
Review the NodeInstallerProgressing status condition for etcd to verify that all nodes are at the latest revision. The output shows AllNodesAtLatestRevision upon successful update:
```
AllNodesAtLatestRevision
3 nodes are at revision 7 (1)
```
1 In this example, the latest revision number is 7.

If the output includes multiple revision numbers, such as 2 nodes are at revision 6; 1 nodes are at revision 7, this means that the update is still in progress. Wait a few minutes and try again.
After etcd is redeployed, force new rollouts for the control plane. The Kubernetes API server will reinstall itself on the other nodes because the kubelet is connected to API servers using an internal load balancer.

In a terminal that has access to the cluster as a cluster-admin user, run the following commands.
1. Update the kubeapiserver:
  $ oc patch kubeapiserver cluster -p='{"spec": {"forceRedeploymentReason": "recovery-'"$( date --rfc-3339=ns )"'"}}' --type=merge
  Verify all nodes are updated to the latest revision.
  $ oc get kubeapiserver -o=jsonpath='{range .items[0].status.conditions[?(@.type=="NodeInstallerProgressing")]}{.reason}{"\n"}{.message}{"\n"}'
  Review the NodeInstallerProgressing status condition to verify that all nodes are at the latest revision. The output shows AllNodesAtLatestRevision upon successful update:
  AllNodesAtLatestRevision 3 nodes are at revision 7 (1)
  1 In this example, the latest revision number is 7.
  
  If the output includes multiple revision numbers, such as 2 nodes are at revision 6; 1 nodes are at revision 7, this means that the update is still in progress. Wait a few minutes and try again.
2. Update the kubecontrollermanager:
  $ oc patch kubecontrollermanager cluster -p='{"spec": {"forceRedeploymentReason": "recovery-'"$( date --rfc-3339=ns )"'"}}' --type=merge
  Verify all nodes are updated to the latest revision.
  $ oc get kubecontrollermanager -o=jsonpath='{range .items[0].status.conditions[?(@.type=="NodeInstallerProgressing")]}{.reason}{"\n"}{.message}{"\n"}'
  Review the NodeInstallerProgressing status condition to verify that all nodes are at the latest revision. The output shows AllNodesAtLatestRevision upon successful update:
  AllNodesAtLatestRevision 3 nodes are at revision 7 (1)
  1 In this example, the latest revision number is 7.
  
  If the output includes multiple revision numbers, such as 2 nodes are at revision 6; 1 nodes are at revision 7, this means that the update is still in progress. Wait a few minutes and try again.
3. Update the kubescheduler:
  $ oc patch kubescheduler cluster -p='{"spec": {"forceRedeploymentReason": "recovery-'"$( date --rfc-3339=ns )"'"}}' --type=merge
  Verify all nodes are updated to the latest revision.
  $ oc get kubescheduler -o=jsonpath='{range .items[0].status.conditions[?(@.type=="NodeInstallerProgressing")]}{.reason}{"\n"}{.message}{"\n"}'
  Review the NodeInstallerProgressing status condition to verify that all nodes are at the latest revision. The output shows AllNodesAtLatestRevision upon successful update:
  AllNodesAtLatestRevision 3 nodes are at revision 7 (1)
  1 In this example, the latest revision number is 7.
  
  If the output includes multiple revision numbers, such as 2 nodes are at revision 6; 1 nodes are at revision 7, this means that the update is still in progress. Wait a few minutes and try again.

Verify that all master hosts have started and joined the cluster.

In a terminal that has access to the cluster as a cluster-admin user, run the following command:

$ oc get pods -n openshift-etcd | grep etcd

example output

etcd-ip-10-0-143-125.ec2.internal                2/2     Running     0          9h
etcd-ip-10-0-154-194.ec2.internal                2/2     Running     0          9h
etcd-ip-10-0-173-171.ec2.internal                2/2     Running     0          9h

Note that it might take several minutes after completing this procedure for all services to be restored. For example, authentication by using oc login might not immediately work until the OAuth server pods are restarted.