In the Certified Kubernetes Administrator (CKA) exam, etcd is the critical component storing the entire cluster state. Mastery of its maintenance is essential.
**Troubleshooting**
If the API server cannot communicate with etcd, the cluster becomes unresponsive. To troubleshoot:
1. **Check Process/…In the Certified Kubernetes Administrator (CKA) exam, etcd is the critical component storing the entire cluster state. Mastery of its maintenance is essential.
**Troubleshooting**
If the API server cannot communicate with etcd, the cluster becomes unresponsive. To troubleshoot:
1. **Check Process/Pod:** If etcd runs as a static pod, ensure the container is running via `crictl ps`. If it is a systemd service, check `systemctl status etcd`.
2. **Verify Health:** Use the command line tool. Ensure `ETCDCTL_API=3` is set. Run `etcdctl endpoint health` and `etcdctl endpoint status --write-out=table`. You must provide TLS flags (`--cacert`, `--cert`, `--key`), typically found in `/etc/kubernetes/pki/etcd`.
3. **Analyze Logs:** Check logs for 'fsync' latency warnings (indicating disk I/O issues) or space quota errors.
**Backup**
Kubernetes does not back up automatically; you must create snapshots.
Command: `ETCDCTL_API=3 etcdctl snapshot save <path-to-backup> [flags]`.
Use the necessary TLS certificates for authentication. Verify the snapshot integrity afterwards using `etcdctl snapshot status <path-to-backup>`.
**Restore**
Restoring is a destructive action for the current state.
1. **Stop Access:** It is often best to stop the static pod or API server to prevent writes.
2. **Restore Command:** Run `etcdctl snapshot restore <path-to-backup> --data-dir <new-directory>`. Do not overwrite the existing data directory; restore to a new path to isolate the restored state.
3. **Update Manifest:** Edit the etcd static pod manifest (usually `/etc/kubernetes/manifests/etcd.yaml`). Change the `hostPath` volume configuration to point to the `<new-directory>` created in the previous step.
4. **Restart:** Kubelet will restart the pod upon manifest modification. Verify the cluster state recovers once the pod is running.
etcd Troubleshooting and Backup Guide
What is etcd and Why is it Important? etcd is a consistent and highly-available key-value store used as the backing store for all Kubernetes cluster data. It is the "brain" of the cluster; without it, the API server cannot retrieve or save state, and the cluster essentially freezes. In the CKA exam, this is a critical topic because a corrupted cluster state requires a restore from backup to recover functionality. Mastery of these commands is essential for Disaster Recovery scenarios.
How it Works etcd typically runs as a static pod on the Control Plane node. It requires strict authentication using TLS certificates. The primary tool for interacting with it is etcdctl.
The workflow generally involves: 1. Backup: Taking a snapshot of the database. 2. Restore: Generating a new data directory from a snapshot file. 3. Reconfiguration: Pointing the etcd static pod to the new restored data directory.
Troubleshooting Common Issues If etcd is failing, check the following: Pod Status: Is the etcd-master pod running? (kubectl get pods -n kube-system) Logs: Check logs for permission denied errors or disk space issues (kubectl logs etcd-master -n kube-system) Endpoint Health: Verify if the cluster member is healthy (etcdctl endpoint health)
How to Answer Questions on etcd in the Exam 1. Locate Certificates: First, inspect the etcd static pod manifest (usually at /etc/kubernetes/manifests/etcd.yaml). Look for --trusted-ca-file, --cert-file, and --key-file. 2. Authenticate: Construct your command using these certificates. To save time, export them as environment variables: export ETCDCTL_API=3 export ETCDCTL_CACERT=/etc/kubernetes/pki/etcd/ca.crt export ETCDCTL_CERT=/etc/kubernetes/pki/etcd/server.crt export ETCDCTL_KEY=/etc/kubernetes/pki/etcd/server.key 3. Snapshot Save: Run etcdctl snapshot save /path/to/backup.db. 4. Snapshot Restore: Run etcdctl snapshot restore /path/to/backup.db --data-dir /var/lib/etcd-restored. Note that you must restore to a new directory, not the existing one. 5. Update Manifest: Edit /etc/kubernetes/manifests/etcd.yaml. Update the hostPath of the volume to point to your new directory (/var/lib/etcd-restored). The kubelet will detect the file change and restart the pod with the restored data.
Exam Tips: Answering Questions on etcd troubleshooting and backup API Version: Always ensure you are using API version 3. If you type etcdctl and see a warning about version 2, export ETCDCTL_API=3 immediately. Use Internal IP: When defining the endpoint, use https://127.0.0.1:2379 if you are on the control plane node to avoid network issues. Volume Mounts: When restoring, the most common mistake is forgetting to update the volumes: hostPath in the static pod YAML. If you don't update this, etcd will restart using the old, potentially corrupted data. Verification: After restoring, wait 60 seconds and run kubectl get pods -n kube-system to ensure the etcd pod is back in a Running state.