Replacing an unhealthy etcd member - Control plane backup and restore | Backup and restore

Prerequisites
Identifying an unhealthy etcd member
Determining the state of the unhealthy etcd member
Replacing the unhealthy etcd member
Additional resources

This document describes the process to replace a single unhealthy etcd member.

This process depends on whether the etcd member is unhealthy because the machine is not running or the node is not ready, or whether it is unhealthy because the etcd pod is crashlooping.

If you have lost the majority of your control plane hosts, follow the disaster recovery procedure to restore to a previous cluster state instead of this procedure.

If the control plane certificates are not valid on the member being replaced, then you must follow the procedure to recover from expired control plane certificates instead of this procedure.

If a control plane node is lost and a new one is created, the etcd cluster Operator handles generating the new TLS certificates and adding the node as an etcd member.

Prerequisites

Take an etcd backup prior to replacing an unhealthy etcd member.

Identifying an unhealthy etcd member

You can identify if your cluster has an unhealthy etcd member.

Prerequisites

Access to the cluster as a user with the cluster-admin role.

Procedure

Check the status of the EtcdMembersAvailable status condition using the following command:

$ oc get etcd -o=jsonpath='{range .items[0].status.conditions[?(@.type=="EtcdMembersAvailable")]}{.message}{"\n"}'

Review the output:
```
2 of 3 members are available, ip-10-0-131-183.ec2.internal is unhealthy
```
This example output shows that the ip-10-0-131-183.ec2.internal etcd member is unhealthy.

Determining the state of the unhealthy etcd member

The steps to replace an unhealthy etcd member depend on which of the following states your etcd member is in:

The machine is not running or the node is not ready
The etcd pod is crashlooping

This procedure determines which state your etcd member is in. This enables you to know which procedure to follow to replace the unhealthy etcd member.

If you are aware that the machine is not running or the node is not ready, but you expect it to return to a healthy state soon, then you do not need to perform a procedure to replace the etcd member. The etcd cluster Operator will automatically sync when the machine or node returns to a healthy state.

Prerequisites

You have access to the cluster as a user with the cluster-admin role.
You have identified an unhealthy etcd member.

Procedure

Determine if the machine is not running:
```
$ oc get machines -A -ojsonpath='{range .items[*]}{@.status.nodeRef.name}{"\t"}{@.status.providerStatus.instanceState}{"\n"}' | grep -v running
```
Example output
```
ip-10-0-131-183.ec2.internal  stopped (1)
```
1 This output lists the node and the status of the node’s machine. If the status is anything other than running, then the machine is not running.

If the machine is not running, then follow the Replacing an unhealthy etcd member whose machine is not running or whose node is not ready procedure.
Determine if the node is not ready.

If either of the following scenarios are true, then the node is not ready.
- If the machine is running, then check whether the node is unreachable:
  $ oc get nodes -o jsonpath='{range .items[*]}{"\n"}{.metadata.name}{"\t"}{range .spec.taints[*]}{.key}{" "}' | grep unreachable
  Example output
  ip-10-0-131-183.ec2.internal node-role.kubernetes.io/master node.kubernetes.io/unreachable node.kubernetes.io/unreachable (1)
  1 If the node is listed with an unreachable taint, then the node is not ready.
- If the node is still reachable, then check whether the node is listed as NotReady:
  $ oc get nodes -l node-role.kubernetes.io/master | grep "NotReady"
  Example output
  ip-10-0-131-183.ec2.internal NotReady master 122m v1.31.3 (1)
  1 If the node is listed as NotReady, then the node is not ready.
If the node is not ready, then follow the Replacing an unhealthy etcd member whose machine is not running or whose node is not ready procedure.

Determine if the etcd pod is crashlooping.

If the machine is running and the node is ready, then check whether the etcd pod is crashlooping.

Verify that all control plane nodes are listed as Ready:

$ oc get nodes -l node-role.kubernetes.io/master

Example output

NAME                           STATUS   ROLES    AGE     VERSION
ip-10-0-131-183.ec2.internal   Ready    master   6h13m   v1.31.3
ip-10-0-164-97.ec2.internal    Ready    master   6h13m   v1.31.3
ip-10-0-154-204.ec2.internal   Ready    master   6h13m   v1.31.3

Check whether the status of an etcd pod is either Error or CrashloopBackoff:

$ oc -n openshift-etcd get pods -l k8s-app=etcd

Example output

etcd-ip-10-0-131-183.ec2.internal                2/3     Error       7          6h9m (1)
etcd-ip-10-0-164-97.ec2.internal                 3/3     Running     0          6h6m
etcd-ip-10-0-154-204.ec2.internal                3/3     Running     0          6h6m

1	Since this status of this pod is `Error`, then the etcd pod is crashlooping.

If the etcd pod is crashlooping, then follow the Replacing an unhealthy etcd member whose etcd pod is crashlooping procedure.

Replacing the unhealthy etcd member

Depending on the state of your unhealthy etcd member, use one of the following procedures:

Replacing an unhealthy etcd member whose machine is not running or whose node is not ready

This procedure details the steps to replace an etcd member that is unhealthy either because the machine is not running or because the node is not ready.

If your cluster uses a control plane machine set, see "Recovering a degraded etcd Operator" in "Troubleshooting the control plane machine set" for a more simple etcd recovery procedure.

Prerequisites

You have identified the unhealthy etcd member.
You have verified that either the machine is not running or the node is not ready.

You must wait if you power off other control plane nodes. The control plane nodes must remain powered off until the replacement of an unhealthy etcd member is complete.
You have access to the cluster as a user with the cluster-admin role.
You have taken an etcd backup.

It is important to take an etcd backup before performing this procedure, so that you can restore your cluster if you experience any issues.

Procedure

Remove the unhealthy member.

Choose a pod that is not on the affected node:

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

$ oc -n openshift-etcd get pods -l k8s-app=etcd

Example output

etcd-ip-10-0-131-183.ec2.internal                3/3     Running     0          123m
etcd-ip-10-0-164-97.ec2.internal                 3/3     Running     0          123m
etcd-ip-10-0-154-204.ec2.internal                3/3     Running     0          124m

Connect to the running etcd container, passing in the name of a pod that is not on the affected node:

In a terminal that has access to the cluster as a cluster-admin user, run the following command:
```
$ oc rsh -n openshift-etcd etcd-ip-10-0-154-204.ec2.internal
```

View the member list:

sh-4.2# etcdctl member list -w table

Example output

+------------------+---------+------------------------------+---------------------------+---------------------------+
|        ID        | STATUS  |             NAME             |        PEER ADDRS         |       CLIENT ADDRS        |
+------------------+---------+------------------------------+---------------------------+---------------------------+
| 6fc1e7c9db35841d | started | ip-10-0-131-183.ec2.internal | https://10.0.131.183:2380 | https://10.0.131.183:2379 |
| 757b6793e2408b6c | started |  ip-10-0-164-97.ec2.internal |  https://10.0.164.97:2380 |  https://10.0.164.97:2379 |
| ca8c2990a0aa29d1 | started | ip-10-0-154-204.ec2.internal | https://10.0.154.204:2380 | https://10.0.154.204:2379 |
+------------------+---------+------------------------------+---------------------------+---------------------------+

Take note of the ID and the name of the unhealthy etcd member, because these values are needed later in the procedure. The $ etcdctl endpoint health command will list the removed member until the procedure of replacement is finished and a new member is added.

Remove the unhealthy etcd member by providing the ID to the etcdctl member remove command:

sh-4.2# etcdctl member remove 6fc1e7c9db35841d

Example output

Member 6fc1e7c9db35841d removed from cluster ead669ce1fbfb346

View the member list again and verify that the member was removed:

sh-4.2# etcdctl member list -w table

Example output

+------------------+---------+------------------------------+---------------------------+---------------------------+
|        ID        | STATUS  |             NAME             |        PEER ADDRS         |       CLIENT ADDRS        |
+------------------+---------+------------------------------+---------------------------+---------------------------+
| 757b6793e2408b6c | started |  ip-10-0-164-97.ec2.internal |  https://10.0.164.97:2380 |  https://10.0.164.97:2379 |
| ca8c2990a0aa29d1 | started | ip-10-0-154-204.ec2.internal | https://10.0.154.204:2380 | https://10.0.154.204:2379 |
+------------------+---------+------------------------------+---------------------------+---------------------------+

You can now exit the node shell.

Turn off the quorum guard by entering the following command:

$ oc patch etcd/cluster --type=merge -p '{"spec": {"unsupportedConfigOverrides": {"useUnsupportedUnsafeNonHANonProductionUnstableEtcd": true}}}'

This command ensures that you can successfully re-create secrets and roll out the static pods.

After you turn off the quorum guard, the cluster might be unreachable for a short time while the remaining etcd instances reboot to reflect the configuration change.

etcd cannot tolerate any additional member failure when running with two members. Restarting either remaining member breaks the quorum and causes downtime in your cluster. The quorum guard protects etcd from restarts due to configuration changes that could cause downtime, so it must be disabled to complete this procedure.

Delete the affected node by running the following command:

$ oc delete node <node_name>

Example command

$ oc delete node ip-10-0-131-183.ec2.internal

Remove the old secrets for the unhealthy etcd member that was removed.

List the secrets for the unhealthy etcd member that was removed.

$ oc get secrets -n openshift-etcd | grep ip-10-0-131-183.ec2.internal (1)

1	Pass in the name of the unhealthy etcd member that you took note of earlier in this procedure.

There is a peer, serving, and metrics secret as shown in the following output:

Example output

etcd-peer-ip-10-0-131-183.ec2.internal              kubernetes.io/tls                     2      47m
etcd-serving-ip-10-0-131-183.ec2.internal           kubernetes.io/tls                     2      47m
etcd-serving-metrics-ip-10-0-131-183.ec2.internal   kubernetes.io/tls                     2      47m

Delete the secrets for the unhealthy etcd member that was removed.

Delete the peer secret:

$ oc delete secret -n openshift-etcd etcd-peer-ip-10-0-131-183.ec2.internal

Delete the serving secret:

$ oc delete secret -n openshift-etcd etcd-serving-ip-10-0-131-183.ec2.internal

Delete the metrics secret:

$ oc delete secret -n openshift-etcd etcd-serving-metrics-ip-10-0-131-183.ec2.internal

Delete and re-create the control plane machine. After this machine is re-created, a new revision is forced and etcd scales up automatically. See "Replacing an unhealthy etcd member whose machine is not running or whose node is not ready" for more information.

If you are running installer-provisioned infrastructure, or you used the Machine API to create your machines, follow these steps. Otherwise, you must create the new master using the same method that was used to originally create it.

Obtain the machine for the unhealthy member.

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

$ oc get machines -n openshift-machine-api -o wide

Example output

NAME                                        PHASE     TYPE        REGION      ZONE         AGE     NODE                           PROVIDERID                              STATE
clustername-8qw5l-master-0                  Running   m4.xlarge   us-east-1   us-east-1a   3h37m   ip-10-0-131-183.ec2.internal   aws:///us-east-1a/i-0ec2782f8287dfb7e   stopped (1)
clustername-8qw5l-master-1                  Running   m4.xlarge   us-east-1   us-east-1b   3h37m   ip-10-0-154-204.ec2.internal   aws:///us-east-1b/i-096c349b700a19631   running
clustername-8qw5l-master-2                  Running   m4.xlarge   us-east-1   us-east-1c   3h37m   ip-10-0-164-97.ec2.internal    aws:///us-east-1c/i-02626f1dba9ed5bba   running
clustername-8qw5l-worker-us-east-1a-wbtgd   Running   m4.large    us-east-1   us-east-1a   3h28m   ip-10-0-129-226.ec2.internal   aws:///us-east-1a/i-010ef6279b4662ced   running
clustername-8qw5l-worker-us-east-1b-lrdxb   Running   m4.large    us-east-1   us-east-1b   3h28m   ip-10-0-144-248.ec2.internal   aws:///us-east-1b/i-0cb45ac45a166173b   running
clustername-8qw5l-worker-us-east-1c-pkg26   Running   m4.large    us-east-1   us-east-1c   3h28m   ip-10-0-170-181.ec2.internal   aws:///us-east-1c/i-06861c00007751b0a   running

1	This is the control plane machine for the unhealthy node, `ip-10-0-131-183.ec2.internal`.

Delete the machine of the unhealthy member:
```
$ oc delete machine -n openshift-machine-api clustername-8qw5l-master-0 (1)
```
1 Specify the name of the control plane machine for the unhealthy node.

A new machine is automatically provisioned after deleting the machine of the unhealthy member.

Verify that a new machine has been created:

$ oc get machines -n openshift-machine-api -o wide

Example output

NAME                                        PHASE          TYPE        REGION      ZONE         AGE     NODE                           PROVIDERID                              STATE
clustername-8qw5l-master-1                  Running        m4.xlarge   us-east-1   us-east-1b   3h37m   ip-10-0-154-204.ec2.internal   aws:///us-east-1b/i-096c349b700a19631   running
clustername-8qw5l-master-2                  Running        m4.xlarge   us-east-1   us-east-1c   3h37m   ip-10-0-164-97.ec2.internal    aws:///us-east-1c/i-02626f1dba9ed5bba   running
clustername-8qw5l-master-3                  Provisioning   m4.xlarge   us-east-1   us-east-1a   85s     ip-10-0-133-53.ec2.internal    aws:///us-east-1a/i-015b0888fe17bc2c8   running (1)
clustername-8qw5l-worker-us-east-1a-wbtgd   Running        m4.large    us-east-1   us-east-1a   3h28m   ip-10-0-129-226.ec2.internal   aws:///us-east-1a/i-010ef6279b4662ced   running
clustername-8qw5l-worker-us-east-1b-lrdxb   Running        m4.large    us-east-1   us-east-1b   3h28m   ip-10-0-144-248.ec2.internal   aws:///us-east-1b/i-0cb45ac45a166173b   running
clustername-8qw5l-worker-us-east-1c-pkg26   Running        m4.large    us-east-1   us-east-1c   3h28m   ip-10-0-170-181.ec2.internal   aws:///us-east-1c/i-06861c00007751b0a   running

1	The new machine, `clustername-8qw5l-master-3` is being created and is ready once the phase changes from `Provisioning` to `Running`.

It might take a few minutes for the new machine to be created. The etcd cluster Operator will automatically sync when the machine or node returns to a healthy state.

Turn the quorum guard back on by entering the following command:

$ oc patch etcd/cluster --type=merge -p '{"spec": {"unsupportedConfigOverrides": null}}'

You can verify that the unsupportedConfigOverrides section is removed from the object by entering this command:
```
$ oc get etcd/cluster -oyaml
```

If you are using single-node OpenShift, restart the node. Otherwise, you might experience the following error in the etcd cluster Operator:

Example output

EtcdCertSignerControllerDegraded: [Operation cannot be fulfilled on secrets "etcd-peer-sno-0": the object has been modified; please apply your changes to the latest version and try again, Operation cannot be fulfilled on secrets "etcd-serving-sno-0": the object has been modified; please apply your changes to the latest version and try again, Operation cannot be fulfilled on secrets "etcd-serving-metrics-sno-0": the object has been modified; please apply your changes to the latest version and try again]

Verification

Verify that all etcd pods are running properly.

In a terminal that has access to the cluster as a cluster-admin user, run the following command:
```
$ oc -n openshift-etcd get pods -l k8s-app=etcd
```
Example output
```
etcd-ip-10-0-133-53.ec2.internal                 3/3     Running     0          7m49s
etcd-ip-10-0-164-97.ec2.internal                 3/3     Running     0          123m
etcd-ip-10-0-154-204.ec2.internal                3/3     Running     0          124m
```
If the output from the previous command only lists two pods, you can manually force an 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.

Verify that there are exactly three etcd members.

Connect to the running etcd container, passing in the name of a pod that was not on the affected node:

In a terminal that has access to the cluster as a cluster-admin user, run the following command:
```
$ oc rsh -n openshift-etcd etcd-ip-10-0-154-204.ec2.internal
```

View the member list:

sh-4.2# etcdctl member list -w table

Example output

+------------------+---------+------------------------------+---------------------------+---------------------------+
|        ID        | STATUS  |             NAME             |        PEER ADDRS         |       CLIENT ADDRS        |
+------------------+---------+------------------------------+---------------------------+---------------------------+
| 5eb0d6b8ca24730c | started |  ip-10-0-133-53.ec2.internal |  https://10.0.133.53:2380 |  https://10.0.133.53:2379 |
| 757b6793e2408b6c | started |  ip-10-0-164-97.ec2.internal |  https://10.0.164.97:2380 |  https://10.0.164.97:2379 |
| ca8c2990a0aa29d1 | started | ip-10-0-154-204.ec2.internal | https://10.0.154.204:2380 | https://10.0.154.204:2379 |
+------------------+---------+------------------------------+---------------------------+---------------------------+

If the output from the previous command lists more than three etcd members, you must carefully remove the unwanted member.

Be sure to remove the correct etcd member; removing a good etcd member might lead to quorum loss.

Additional resources

Replacing an unhealthy etcd member whose etcd pod is crashlooping

This procedure details the steps to replace an etcd member that is unhealthy because the etcd pod is crashlooping.

Prerequisites

You have identified the unhealthy etcd member.
You have verified that the etcd pod is crashlooping.
You have access to the cluster as a user with the cluster-admin role.
You have taken an etcd backup.

It is important to take an etcd backup before performing this procedure so that your cluster can be restored if you encounter any issues.

Procedure

Stop the crashlooping etcd pod.
1. Debug the node that is crashlooping.
  
  In a terminal that has access to the cluster as a cluster-admin user, run the following command:
  $ oc debug node/ip-10-0-131-183.ec2.internal (1)
  1 Replace this with the name of the unhealthy node.
2. Change your root directory to /host:
  sh-4.2# chroot /host
3. Move the existing etcd pod file out of the kubelet manifest directory:
  sh-4.2# mkdir /var/lib/etcd-backup
  sh-4.2# mv /etc/kubernetes/manifests/etcd-pod.yaml /var/lib/etcd-backup/
4. Move the etcd data directory to a different location:
  sh-4.2# mv /var/lib/etcd/ /tmp
  You can now exit the node shell.

Remove the unhealthy member.

Choose a pod that is not on the affected node.

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

$ oc -n openshift-etcd get pods -l k8s-app=etcd

Example output

etcd-ip-10-0-131-183.ec2.internal                2/3     Error       7          6h9m
etcd-ip-10-0-164-97.ec2.internal                 3/3     Running     0          6h6m
etcd-ip-10-0-154-204.ec2.internal                3/3     Running     0          6h6m

Connect to the running etcd container, passing in the name of a pod that is not on the affected node.

In a terminal that has access to the cluster as a cluster-admin user, run the following command:
```
$ oc rsh -n openshift-etcd etcd-ip-10-0-154-204.ec2.internal
```

View the member list:

sh-4.2# etcdctl member list -w table

Example output

+------------------+---------+------------------------------+---------------------------+---------------------------+
|        ID        | STATUS  |             NAME             |        PEER ADDRS         |       CLIENT ADDRS        |
+------------------+---------+------------------------------+---------------------------+---------------------------+
| 62bcf33650a7170a | started | ip-10-0-131-183.ec2.internal | https://10.0.131.183:2380 | https://10.0.131.183:2379 |
| b78e2856655bc2eb | started |  ip-10-0-164-97.ec2.internal |  https://10.0.164.97:2380 |  https://10.0.164.97:2379 |
| d022e10b498760d5 | started | ip-10-0-154-204.ec2.internal | https://10.0.154.204:2380 | https://10.0.154.204:2379 |
+------------------+---------+------------------------------+---------------------------+---------------------------+

Take note of the ID and the name of the unhealthy etcd member, because these values are needed later in the procedure.

Remove the unhealthy etcd member by providing the ID to the etcdctl member remove command:

sh-4.2# etcdctl member remove 62bcf33650a7170a

Example output

Member 62bcf33650a7170a removed from cluster ead669ce1fbfb346

View the member list again and verify that the member was removed:

sh-4.2# etcdctl member list -w table

Example output

+------------------+---------+------------------------------+---------------------------+---------------------------+
|        ID        | STATUS  |             NAME             |        PEER ADDRS         |       CLIENT ADDRS        |
+------------------+---------+------------------------------+---------------------------+---------------------------+
| b78e2856655bc2eb | started |  ip-10-0-164-97.ec2.internal |  https://10.0.164.97:2380 |  https://10.0.164.97:2379 |
| d022e10b498760d5 | started | ip-10-0-154-204.ec2.internal | https://10.0.154.204:2380 | https://10.0.154.204:2379 |
+------------------+---------+------------------------------+---------------------------+---------------------------+

You can now exit the node shell.

Turn off the quorum guard by entering the following command:
```
$ oc patch etcd/cluster --type=merge -p '{"spec": {"unsupportedConfigOverrides": {"useUnsupportedUnsafeNonHANonProductionUnstableEtcd": true}}}'
```
This command ensures that you can successfully re-create secrets and roll out the static pods.

Remove the old secrets for the unhealthy etcd member that was removed.

List the secrets for the unhealthy etcd member that was removed.

$ oc get secrets -n openshift-etcd | grep ip-10-0-131-183.ec2.internal (1)

1	Pass in the name of the unhealthy etcd member that you took note of earlier in this procedure.

There is a peer, serving, and metrics secret as shown in the following output:

Example output

etcd-peer-ip-10-0-131-183.ec2.internal              kubernetes.io/tls                     2      47m
etcd-serving-ip-10-0-131-183.ec2.internal           kubernetes.io/tls                     2      47m
etcd-serving-metrics-ip-10-0-131-183.ec2.internal   kubernetes.io/tls                     2      47m

Delete the secrets for the unhealthy etcd member that was removed.

Delete the peer secret:

$ oc delete secret -n openshift-etcd etcd-peer-ip-10-0-131-183.ec2.internal

Delete the serving secret:

$ oc delete secret -n openshift-etcd etcd-serving-ip-10-0-131-183.ec2.internal

Delete the metrics secret:

$ oc delete secret -n openshift-etcd etcd-serving-metrics-ip-10-0-131-183.ec2.internal

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": "single-master-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, it ensures that all control plane nodes have a functioning etcd pod.

Turn the quorum guard back on by entering the following command:

$ oc patch etcd/cluster --type=merge -p '{"spec": {"unsupportedConfigOverrides": null}}'

You can verify that the unsupportedConfigOverrides section is removed from the object by entering this command:
```
$ oc get etcd/cluster -oyaml
```

If you are using single-node OpenShift, restart the node. Otherwise, you might encounter the following error in the etcd cluster Operator:

Example output

EtcdCertSignerControllerDegraded: [Operation cannot be fulfilled on secrets "etcd-peer-sno-0": the object has been modified; please apply your changes to the latest version and try again, Operation cannot be fulfilled on secrets "etcd-serving-sno-0": the object has been modified; please apply your changes to the latest version and try again, Operation cannot be fulfilled on secrets "etcd-serving-metrics-sno-0": the object has been modified; please apply your changes to the latest version and try again]

Verification

Verify that the new member is available and healthy.

Connect to the running etcd container again.

In a terminal that has access to the cluster as a cluster-admin user, run the following command:
```
$ oc rsh -n openshift-etcd etcd-ip-10-0-154-204.ec2.internal
```

Verify that all members are healthy:

sh-4.2# etcdctl endpoint health

Example output

https://10.0.131.183:2379 is healthy: successfully committed proposal: took = 16.671434ms
https://10.0.154.204:2379 is healthy: successfully committed proposal: took = 16.698331ms
https://10.0.164.97:2379 is healthy: successfully committed proposal: took = 16.621645ms

Replacing an unhealthy bare metal etcd member whose machine is not running or whose node is not ready

This procedure details the steps to replace a bare metal etcd member that is unhealthy either because the machine is not running or because the node is not ready.

If you are running installer-provisioned infrastructure or you used the Machine API to create your machines, follow these steps. Otherwise you must create the new control plane node using the same method that was used to originally create it.

Prerequisites

You have identified the unhealthy bare metal etcd member.
You have verified that either the machine is not running or the node is not ready.
You have access to the cluster as a user with the cluster-admin role.
You have taken an etcd backup.

You must take an etcd backup before performing this procedure so that your cluster can be restored if you encounter any issues.

Procedure

Verify and remove the unhealthy member.

Choose a pod that is not on the affected node:

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

$ oc -n openshift-etcd get pods -l k8s-app=etcd -o wide

Example output

etcd-openshift-control-plane-0   5/5   Running   11   3h56m   192.168.10.9   openshift-control-plane-0  <none>           <none>
etcd-openshift-control-plane-1   5/5   Running   0    3h54m   192.168.10.10   openshift-control-plane-1   <none>           <none>
etcd-openshift-control-plane-2   5/5   Running   0    3h58m   192.168.10.11   openshift-control-plane-2   <none>           <none>

Connect to the running etcd container, passing in the name of a pod that is not on the affected node:

In a terminal that has access to the cluster as a cluster-admin user, run the following command:
```
$ oc rsh -n openshift-etcd etcd-openshift-control-plane-0
```

View the member list:

sh-4.2# etcdctl member list -w table

Example output

+------------------+---------+--------------------+---------------------------+---------------------------+---------------------+
| ID               | STATUS  | NAME                      | PEER ADDRS                  | CLIENT ADDRS                | IS LEARNER |
+------------------+---------+--------------------+---------------------------+---------------------------+---------------------+
| 7a8197040a5126c8 | started | openshift-control-plane-2 | https://192.168.10.11:2380/ | https://192.168.10.11:2379/ | false |
| 8d5abe9669a39192 | started | openshift-control-plane-1 | https://192.168.10.10:2380/ | https://192.168.10.10:2379/ | false |
| cc3830a72fc357f9 | started | openshift-control-plane-0 | https://192.168.10.9:2380/ | https://192.168.10.9:2379/   | false |
+------------------+---------+--------------------+---------------------------+---------------------------+---------------------+

Take note of the ID and the name of the unhealthy etcd member, because these values are required later in the procedure. The etcdctl endpoint health command will list the removed member until the replacement procedure is completed and the new member is added.

Remove the unhealthy etcd member by providing the ID to the etcdctl member remove command:

Be sure to remove the correct etcd member; removing a good etcd member might lead to quorum loss.
```
sh-4.2# etcdctl member remove 7a8197040a5126c8
```
Example output
```
Member 7a8197040a5126c8 removed from cluster b23536c33f2cdd1b
```

View the member list again and verify that the member was removed:

sh-4.2# etcdctl member list -w table

Example output

+------------------+---------+--------------------+---------------------------+---------------------------+-------------------------+
| ID               | STATUS  | NAME                      | PEER ADDRS                  | CLIENT ADDRS                | IS LEARNER |
+------------------+---------+--------------------+---------------------------+---------------------------+-------------------------+
| cc3830a72fc357f9 | started | openshift-control-plane-2 | https://192.168.10.11:2380/ | https://192.168.10.11:2379/ | false |
| 8d5abe9669a39192 | started | openshift-control-plane-1 | https://192.168.10.10:2380/ | https://192.168.10.10:2379/ | false |
+------------------+---------+--------------------+---------------------------+---------------------------+-------------------------+

You can now exit the node shell.

After you remove the member, the cluster might be unreachable for a short time while the remaining etcd instances reboot.

Turn off the quorum guard by entering the following command:
```
$ oc patch etcd/cluster --type=merge -p '{"spec": {"unsupportedConfigOverrides": {"useUnsupportedUnsafeNonHANonProductionUnstableEtcd": true}}}'
```
This command ensures that you can successfully re-create secrets and roll out the static pods.

Remove the old secrets for the unhealthy etcd member that was removed by running the following commands.

List the secrets for the unhealthy etcd member that was removed.

$ oc get secrets -n openshift-etcd | grep openshift-control-plane-2

Pass in the name of the unhealthy etcd member that you took note of earlier in this procedure.

There is a peer, serving, and metrics secret as shown in the following output:

etcd-peer-openshift-control-plane-2             kubernetes.io/tls   2   134m
etcd-serving-metrics-openshift-control-plane-2  kubernetes.io/tls   2   134m
etcd-serving-openshift-control-plane-2          kubernetes.io/tls   2   134m

Delete the secrets for the unhealthy etcd member that was removed.

Delete the peer secret:

$ oc delete secret etcd-peer-openshift-control-plane-2 -n openshift-etcd

secret "etcd-peer-openshift-control-plane-2" deleted

Delete the serving secret:

$ oc delete secret etcd-serving-metrics-openshift-control-plane-2 -n openshift-etcd

secret "etcd-serving-metrics-openshift-control-plane-2" deleted

Delete the metrics secret:

$ oc delete secret etcd-serving-openshift-control-plane-2 -n openshift-etcd

secret "etcd-serving-openshift-control-plane-2" deleted

Obtain the machine for the unhealthy member.

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

$ oc get machines -n openshift-machine-api -o wide

Example output

NAME                              PHASE     TYPE   REGION   ZONE   AGE     NODE                               PROVIDERID                                                                                              STATE
examplecluster-control-plane-0    Running                          3h11m   openshift-control-plane-0   baremetalhost:///openshift-machine-api/openshift-control-plane-0/da1ebe11-3ff2-41c5-b099-0aa41222964e   externally provisioned (1)
examplecluster-control-plane-1    Running                          3h11m   openshift-control-plane-1   baremetalhost:///openshift-machine-api/openshift-control-plane-1/d9f9acbc-329c-475e-8d81-03b20280a3e1   externally provisioned
examplecluster-control-plane-2    Running                          3h11m   openshift-control-plane-2   baremetalhost:///openshift-machine-api/openshift-control-plane-2/3354bdac-61d8-410f-be5b-6a395b056135   externally provisioned
examplecluster-compute-0          Running                          165m    openshift-compute-0         baremetalhost:///openshift-machine-api/openshift-compute-0/3d685b81-7410-4bb3-80ec-13a31858241f         provisioned
examplecluster-compute-1          Running                          165m    openshift-compute-1         baremetalhost:///openshift-machine-api/openshift-compute-1/0fdae6eb-2066-4241-91dc-e7ea72ab13b9         provisioned

1	This is the control plane machine for the unhealthy node, `examplecluster-control-plane-2`.

Ensure that the Bare Metal Operator is available by running the following command:

$ oc get clusteroperator baremetal

Example output

NAME        VERSION   AVAILABLE   PROGRESSING   DEGRADED   SINCE   MESSAGE
baremetal   4.0    True        False         False      3d15h

Remove the old BareMetalHost object by running the following command:

$ oc delete bmh openshift-control-plane-2 -n openshift-machine-api

Example output

baremetalhost.metal3.io "openshift-control-plane-2" deleted

Delete the machine of the unhealthy member by running the following command:
```
$ oc delete machine -n openshift-machine-api examplecluster-control-plane-2
```
After you remove the BareMetalHost and Machine objects, then the Machine controller automatically deletes the Node object.

If deletion of the machine is delayed for any reason or the command is obstructed and delayed, you can force deletion by removing the machine object finalizer field.

Do not interrupt machine deletion by pressing Ctrl+c. You must allow the command to proceed to completion. Open a new terminal window to edit and delete the finalizer fields.

A new machine is automatically provisioned after deleting the machine of the unhealthy member.
1. Edit the machine configuration by running the following command:
  $ oc edit machine -n openshift-machine-api examplecluster-control-plane-2
2. Delete the following fields in the Machine custom resource, and then save the updated file:
  finalizers: - machine.machine.openshift.io
  Example output
  machine.machine.openshift.io/examplecluster-control-plane-2 edited

Verify that the machine was deleted by running the following command:

$ oc get machines -n openshift-machine-api -o wide

Example output

NAME                              PHASE     TYPE   REGION   ZONE   AGE     NODE                                 PROVIDERID                                                                                       STATE
examplecluster-control-plane-0    Running                          3h11m   openshift-control-plane-0   baremetalhost:///openshift-machine-api/openshift-control-plane-0/da1ebe11-3ff2-41c5-b099-0aa41222964e   externally provisioned
examplecluster-control-plane-1    Running                          3h11m   openshift-control-plane-1   baremetalhost:///openshift-machine-api/openshift-control-plane-1/d9f9acbc-329c-475e-8d81-03b20280a3e1   externally provisioned
examplecluster-compute-0          Running                          165m    openshift-compute-0         baremetalhost:///openshift-machine-api/openshift-compute-0/3d685b81-7410-4bb3-80ec-13a31858241f         provisioned
examplecluster-compute-1          Running                          165m    openshift-compute-1         baremetalhost:///openshift-machine-api/openshift-compute-1/0fdae6eb-2066-4241-91dc-e7ea72ab13b9         provisioned

Verify that the node has been deleted by running the following command:

$ oc get nodes

NAME                     STATUS ROLES   AGE   VERSION
openshift-control-plane-0 Ready master 3h24m v1.31.3
openshift-control-plane-1 Ready master 3h24m v1.31.3
openshift-compute-0       Ready worker 176m v1.31.3
openshift-compute-1       Ready worker 176m v1.31.3

Create the new BareMetalHost object and the secret to store the BMC credentials:

$ cat <<EOF | oc apply -f -
apiVersion: v1
kind: Secret
metadata:
  name: openshift-control-plane-2-bmc-secret
  namespace: openshift-machine-api
data:
  password: <password>
  username: <username>
type: Opaque
---
apiVersion: metal3.io/v1alpha1
kind: BareMetalHost
metadata:
  name: openshift-control-plane-2
  namespace: openshift-machine-api
spec:
  automatedCleaningMode: disabled
  bmc:
    address: redfish://10.46.61.18:443/redfish/v1/Systems/1
    credentialsName: openshift-control-plane-2-bmc-secret
    disableCertificateVerification: true
  bootMACAddress: 48:df:37:b0:8a:a0
  bootMode: UEFI
  externallyProvisioned: false
  online: true
  rootDeviceHints:
    deviceName: /dev/disk/by-id/scsi-<serial_number>
  userData:
    name: master-user-data-managed
    namespace: openshift-machine-api
EOF

The username and password can be found from the other bare metal host’s secrets. The protocol to use in bmc:address can be taken from other bmh objects.

If you reuse the BareMetalHost object definition from an existing control plane host, do not leave the externallyProvisioned field set to true.

Existing control plane BareMetalHost objects may have the externallyProvisioned flag set to true if they were provisioned by the OKD installation program.

After the inspection is complete, the BareMetalHost object is created and available to be provisioned.

Verify the creation process using available BareMetalHost objects:

$ oc get bmh -n openshift-machine-api

NAME                      STATE                  CONSUMER                      ONLINE ERROR   AGE
openshift-control-plane-0 externally provisioned examplecluster-control-plane-0 true         4h48m
openshift-control-plane-1 externally provisioned examplecluster-control-plane-1 true         4h48m
openshift-control-plane-2 available              examplecluster-control-plane-3 true         47m
openshift-compute-0       provisioned            examplecluster-compute-0       true         4h48m
openshift-compute-1       provisioned            examplecluster-compute-1       true         4h48m

Verify that a new machine has been created:

$ oc get machines -n openshift-machine-api -o wide

Example output

NAME                                   PHASE     TYPE   REGION   ZONE   AGE     NODE                              PROVIDERID                                                                                            STATE
examplecluster-control-plane-0         Running                          3h11m   openshift-control-plane-0   baremetalhost:///openshift-machine-api/openshift-control-plane-0/da1ebe11-3ff2-41c5-b099-0aa41222964e   externally provisioned (1)
examplecluster-control-plane-1         Running                          3h11m   openshift-control-plane-1   baremetalhost:///openshift-machine-api/openshift-control-plane-1/d9f9acbc-329c-475e-8d81-03b20280a3e1   externally provisioned
examplecluster-control-plane-2         Running                          3h11m   openshift-control-plane-2   baremetalhost:///openshift-machine-api/openshift-control-plane-2/3354bdac-61d8-410f-be5b-6a395b056135   externally provisioned
examplecluster-compute-0               Running                          165m    openshift-compute-0         baremetalhost:///openshift-machine-api/openshift-compute-0/3d685b81-7410-4bb3-80ec-13a31858241f         provisioned
examplecluster-compute-1               Running                          165m    openshift-compute-1         baremetalhost:///openshift-machine-api/openshift-compute-1/0fdae6eb-2066-4241-91dc-e7ea72ab13b9         provisioned

1	The new machine, `clustername-8qw5l-master-3` is being created and is ready after the phase changes from `Provisioning` to `Running`.

It should take a few minutes for the new machine to be created. The etcd cluster Operator will automatically sync when the machine or node returns to a healthy state.

Verify that the bare metal host becomes provisioned and no error reported by running the following command:

$ oc get bmh -n openshift-machine-api

Example output

$ oc get bmh -n openshift-machine-api
NAME                      STATE                  CONSUMER                       ONLINE ERROR AGE
openshift-control-plane-0 externally provisioned examplecluster-control-plane-0 true         4h48m
openshift-control-plane-1 externally provisioned examplecluster-control-plane-1 true         4h48m
openshift-control-plane-2 provisioned            examplecluster-control-plane-3 true          47m
openshift-compute-0       provisioned            examplecluster-compute-0       true         4h48m
openshift-compute-1       provisioned            examplecluster-compute-1       true         4h48m

Verify that the new node is added and in a ready state by running this command:

$ oc get nodes

Example output

$ oc get nodes
NAME                     STATUS ROLES   AGE   VERSION
openshift-control-plane-0 Ready master 4h26m v1.31.3
openshift-control-plane-1 Ready master 4h26m v1.31.3
openshift-control-plane-2 Ready master 12m   v1.31.3
openshift-compute-0       Ready worker 3h58m v1.31.3
openshift-compute-1       Ready worker 3h58m v1.31.3

Turn the quorum guard back on by entering the following command:

$ oc patch etcd/cluster --type=merge -p '{"spec": {"unsupportedConfigOverrides": null}}'

You can verify that the unsupportedConfigOverrides section is removed from the object by entering this command:
```
$ oc get etcd/cluster -oyaml
```

If you are using single-node OpenShift, restart the node. Otherwise, you might encounter the following error in the etcd cluster Operator:

Example output

EtcdCertSignerControllerDegraded: [Operation cannot be fulfilled on secrets "etcd-peer-sno-0": the object has been modified; please apply your changes to the latest version and try again, Operation cannot be fulfilled on secrets "etcd-serving-sno-0": the object has been modified; please apply your changes to the latest version and try again, Operation cannot be fulfilled on secrets "etcd-serving-metrics-sno-0": the object has been modified; please apply your changes to the latest version and try again]

Verification

Verify that all etcd pods are running properly.

In a terminal that has access to the cluster as a cluster-admin user, run the following command:
```
$ oc -n openshift-etcd get pods -l k8s-app=etcd
```
Example output
```
etcd-openshift-control-plane-0      5/5     Running     0     105m
etcd-openshift-control-plane-1      5/5     Running     0     107m
etcd-openshift-control-plane-2      5/5     Running     0     103m
```
If the output from the previous command only lists two pods, you can manually force an 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.

To verify there are exactly three etcd members, connect to the running etcd container, passing in the name of a pod that was not on the affected node. In a terminal that has access to the cluster as a cluster-admin user, run the following command:
```
$ oc rsh -n openshift-etcd etcd-openshift-control-plane-0
```

View the member list:

sh-4.2# etcdctl member list -w table

Example output

+------------------+---------+--------------------+---------------------------+---------------------------+-----------------+
|        ID        | STATUS  |        NAME        |        PEER ADDRS         |       CLIENT ADDRS        |    IS LEARNER    |
+------------------+---------+--------------------+---------------------------+---------------------------+-----------------+
| 7a8197040a5126c8 | started | openshift-control-plane-2 | https://192.168.10.11:2380 | https://192.168.10.11:2379 |   false |
| 8d5abe9669a39192 | started | openshift-control-plane-1 | https://192.168.10.10:2380 | https://192.168.10.10:2379 |   false |
| cc3830a72fc357f9 | started | openshift-control-plane-0 | https://192.168.10.9:2380 | https://192.168.10.9:2379 |     false |
+------------------+---------+--------------------+---------------------------+---------------------------+-----------------+

If the output from the previous command lists more than three etcd members, you must carefully remove the unwanted member.

Verify that all etcd members are healthy by running the following command:

# etcdctl endpoint health --cluster

Example output

https://192.168.10.10:2379 is healthy: successfully committed proposal: took = 8.973065ms
https://192.168.10.9:2379 is healthy: successfully committed proposal: took = 11.559829ms
https://192.168.10.11:2379 is healthy: successfully committed proposal: took = 11.665203ms

Validate that all nodes are at the latest revision by running the following command:

$ oc get etcd -o=jsonpath='{range.items[0].status.conditions[?(@.type=="NodeInstallerProgressing")]}{.reason}{"\n"}{.message}{"\n"}'

AllNodesAtLatestRevision

Additional resources

Quorum protection with machine lifecycle hooks