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Backing up etcd

etcd is the key-value store for OpenShift Container Platform, which persists the state of all resource objects.

Back up your cluster’s etcd data regularly and store in a secure location ideally outside the OpenShift Container Platform environment. Do not take an etcd backup before the first certificate rotation completes, which occurs 24 hours after installation, otherwise the backup will contain expired certificates. It is also recommended to take etcd backups during non-peak usage hours because the etcd snapshot has a high I/O cost.

Be sure to take an etcd backup before you update your cluster. Taking a backup before you update is important because 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 4.17.5 cluster must use an etcd backup that was taken from 4.17.5.

Back up your cluster’s etcd data by performing a single invocation of the backup script on a control plane host. Do not take a backup for each control plane host.

After you have an etcd backup, you can restore to a previous cluster state.

Backing up etcd data

Follow these steps to back up etcd data by creating an etcd snapshot and backing up the resources for the static pods. This backup can be saved and used at a later time if you need to restore etcd.

Only save a backup from a single control plane host. Do not take a backup from each control plane host in the cluster.
Prerequisites

  • You have access to the cluster as a user with the cluster-admin role.

  • You have checked whether the cluster-wide proxy is enabled.

    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.
Procedure

  1. Start a debug session as root for a control plane node:

    $ oc debug --as-root node/<node_name>

  2. Change your root directory to /host in the debug shell:

    sh-4.4# chroot /host

  3. If the cluster-wide proxy is enabled, export the NO_PROXY, HTTP_PROXY, and HTTPS_PROXY environment variables by running the following commands:

    $ export HTTP_PROXY=http://<your_proxy.example.com>:8080
    $ export HTTPS_PROXY=https://<your_proxy.example.com>:8080
    $ export NO_PROXY=<example.com>

  4. Run the cluster-backup.sh script in the debug shell and pass in the location to save the backup to.

    The cluster-backup.sh script is maintained as a component of the etcd Cluster Operator and is a wrapper around the etcdctl snapshot save command.

    		 
    sh-4.4# /usr/local/bin/cluster-backup.sh /home/core/assets/backup
    Example script output
    found latest kube-apiserver: /etc/kubernetes/static-pod-resources/kube-apiserver-pod-6
found latest kube-controller-manager: /etc/kubernetes/static-pod-resources/kube-controller-manager-pod-7
found latest kube-scheduler: /etc/kubernetes/static-pod-resources/kube-scheduler-pod-6
found latest etcd: /etc/kubernetes/static-pod-resources/etcd-pod-3
ede95fe6b88b87ba86a03c15e669fb4aa5bf0991c180d3c6895ce72eaade54a1
etcdctl version: 3.4.14
API version: 3.4
{"level":"info","ts":1624647639.0188997,"caller":"snapshot/v3_snapshot.go:119","msg":"created temporary db file","path":"/home/core/assets/backup/snapshot_2021-06-25_190035.db.part"}
{"level":"info","ts":"2021-06-25T19:00:39.030Z","caller":"clientv3/maintenance.go:200","msg":"opened snapshot stream; downloading"}
{"level":"info","ts":1624647639.0301006,"caller":"snapshot/v3_snapshot.go:127","msg":"fetching snapshot","endpoint":"https://10.0.0.5:2379"}
{"level":"info","ts":"2021-06-25T19:00:40.215Z","caller":"clientv3/maintenance.go:208","msg":"completed snapshot read; closing"}
{"level":"info","ts":1624647640.6032252,"caller":"snapshot/v3_snapshot.go:142","msg":"fetched snapshot","endpoint":"https://10.0.0.5:2379","size":"114 MB","took":1.584090459}
{"level":"info","ts":1624647640.6047094,"caller":"snapshot/v3_snapshot.go:152","msg":"saved","path":"/home/core/assets/backup/snapshot_2021-06-25_190035.db"}
Snapshot saved at /home/core/assets/backup/snapshot_2021-06-25_190035.db
{"hash":3866667823,"revision":31407,"totalKey":12828,"totalSize":114446336}
snapshot db and kube resources are successfully saved to /home/core/assets/backup

    In this example, two files are created in the /home/core/assets/backup/ directory on the control plane host:

    • snapshot_<datetimestamp>.db: This file is the etcd snapshot. The cluster-backup.sh script confirms its validity.

    • static_kuberesources_<datetimestamp>.tar.gz: This file contains the resources for the static pods. If etcd encryption is enabled, it also contains the encryption keys for the etcd snapshot.

      If etcd encryption is enabled, it is recommended to store this second file separately from the etcd snapshot for security reasons. However, this file is required to restore from the etcd snapshot.

      Keep in mind that etcd encryption only encrypts values, not keys. This means that resource types, namespaces, and object names are unencrypted.

Additional resources

Creating automated etcd backups

The automated backup feature for etcd supports both recurring and single backups. Recurring backups create a cron job that starts a single backup each time the job triggers.

Automating etcd backups is a Technology Preview feature only. Technology Preview features are not supported with Red Hat production service level agreements (SLAs) and might not be functionally complete. Red Hat does not recommend using them in production. These features provide early access to upcoming product features, enabling customers to test functionality and provide feedback during the development process.

For more information about the support scope of Red Hat Technology Preview features, see Technology Preview Features Support Scope.

Enabling automated etcd backups

Follow these steps to enable automated backups for etcd.

Enabling the TechPreviewNoUpgrade feature set on your cluster prevents minor version updates. The TechPreviewNoUpgrade feature set cannot be disabled. Do not enable this feature set on production clusters.
Prerequisites

  • You have access to the cluster as a user with the cluster-admin role.

  • You have access to the OpenShift CLI (oc).

Procedure

  1. Create a FeatureGate custom resource (CR) file named enable-tech-preview-no-upgrade.yaml with the following contents:

    apiVersion: config.openshift.io/v1
kind: FeatureGate
metadata:
  name: cluster
spec:
  featureSet: TechPreviewNoUpgrade

  2. Apply the CR and enable automated backups:

    $ oc apply -f enable-tech-preview-no-upgrade.yaml

  3. It takes time to enable the related APIs. Verify the creation of the custom resource definition (CRD) by running the following command:

    $ oc get crd | grep backup
    Example output
    backups.config.openshift.io 2023-10-25T13:32:43Z
etcdbackups.operator.openshift.io 2023-10-25T13:32:04Z

Creating a single etcd backup

Follow these steps to create a single etcd backup by creating and applying a custom resource (CR).

Prerequisites

  • You have access to the cluster as a user with the cluster-admin role.

  • You have access to the OpenShift CLI (oc).

  • You have a PVC to save backup data to.

Procedure

  1. Create a CR file named etcd-single-backup.yaml with contents such as the following example:

    apiVersion: operator.openshift.io/v1alpha1
kind: EtcdBackup
metadata:
  name: etcd-single-backup
  namespace: openshift-etcd
spec:
  pvcName: etcd-backup-pvc (1)
    1 The name of the persistent volume claim (PVC) to save the backup to. Adjust this value according to your environment.

  2. Apply the CR to start a single backup:

    $ oc apply -f etcd-single-backup.yaml

Creating recurring etcd backups

Follow these steps to create automated recurring backups of etcd.

Use dynamically-provisioned storage to keep the created etcd backup data in a safe, external location if possible. If dynamically-provisioned storage is not available, consider storing the backup data on an NFS share to make backup recovery more accessible.

Prerequisites

  • You have access to the cluster as a user with the cluster-admin role.

  • You have access to the OpenShift CLI (oc).

Procedure

  1. If dynamically-provisioned storage is available, complete the following steps to create automated recurring backups:

    1. Create a persistent volume claim (PVC) named etcd-backup-pvc.yaml with contents such as the following example:

      kind: PersistentVolumeClaim
apiVersion: v1
metadata:
  name: etcd-backup-pvc
  namespace: openshift-etcd
spec:
  accessModes:
    - ReadWriteOnce
  resources:
    requests:
      storage: 200Gi (1)
  storageClassName: standard-csi (2)
  volumeMode: Filesystem
      1 The amount of storage available to the PVC. Adjust this value for your requirements.
      2 The name of the StorageClass required by the claim. Adjust this value according to your environment.

      Each of the following providers require changes to the accessModes and storageClassName keys:

      Provider accessModes value storageClassName value

      AWS with the versioned-installer-efc_operator-ci profile

      - ReadWriteMany

      efs-sc

      Google Cloud Platform

      - ReadWriteMany

      filestore-csi

      Microsoft Azure

      - ReadWriteMany

      azurefile-csi

    2. Apply the PVC by running the following command:

      $ oc apply -f etcd-backup-pvc.yaml

    3. Verify the creation of the PVC by running the following command:

      $ oc get pvc
      Example output
      NAME              STATUS    VOLUME   CAPACITY   ACCESS MODES   STORAGECLASS   AGE
etcd-backup-pvc   Pending                                      standard-csi   51s

      Dynamic PVCs stay in the Pending state until they are mounted.

  2. If dynamically-provisioned storage is unavailable, create a local storage PVC by completing the following steps:

    If you delete or otherwise lose access to the node that contains the stored backup data, you can lose data.

    1. Create a StorageClass CR file named etcd-backup-local-storage.yaml with the following contents:

      apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
  name: etcd-backup-local-storage
provisioner: kubernetes.io/no-provisioner
volumeBindingMode: WaitForFirstConsumer

    2. Apply the StorageClass CR by running the following command:

      $ oc apply -f etcd-backup-local-storage.yaml

    3. Create a PV named etcd-backup-pv-fs.yaml from the applied StorageClass with content such as the following example:

      apiVersion: v1
kind: PersistentVolume
metadata:
  name: etcd-backup-pv-fs
spec:
  capacity:
    storage: 100Gi (1)
  volumeMode: Filesystem
  accessModes:
  - ReadWriteMany
  persistentVolumeReclaimPolicy: Delete
  storageClassName: local-storage
  local:
    path: /mnt/
  nodeAffinity:
    required:
      nodeSelectorTerms:
      - matchExpressions:
        - key: kubernetes.io/hostname
          operator: In
          values:
          - <example-master-node> (2)
      1 The amount of storage available to the PV. Adjust this value for your requirements.
      2 Replace this value with the node to attach this PV to.

      Run the following command to list the available nodes:

      $ oc get nodes

    4. Verify the creation of the PV by running the following command:

      $ oc get pv
      Example output
      NAME                    CAPACITY   ACCESS MODES   RECLAIM POLICY   STATUS      CLAIM   STORAGECLASS    REASON   AGE
etcd-backup-pv-fs       100Gi      RWX            Delete           Available           local-storage            10s

    5. Create a PVC named etcd-backup-pvc.yaml with contents such as the following example:

      kind: PersistentVolumeClaim
apiVersion: v1
metadata:
  name: etcd-backup-pvc
spec:
  accessModes:
  - ReadWriteMany
  volumeMode: Filesystem
  resources:
    requests:
      storage: 10Gi (1)
  storageClassName: local-storage
      1 The amount of storage available to the PVC. Adjust this value for your requirements.

    6. Apply the PVC by running the following command:

      $ oc apply -f etcd-backup-pvc.yaml

  3. Create a custom resource definition (CRD) file named etcd-recurring-backups.yaml. The contents of the created CRD define the schedule and retention type of automated backups.

    For the default retention type of RetentionNumber with 15 retained backups, use contents such as the following example:

    apiVersion: config.openshift.io/v1alpha1
kind: Backup
metadata:
  name: etcd-recurring-backup
spec:
  etcd:
    schedule: "20 4 * * *" (1)
    timeZone: "UTC"
    pvcName: etcd-backup-pvc
    1 The CronTab schedule for recurring backups. Adjust this value for your needs.

    To use retention based on the maximum number of backups, add the following key-value pairs to the etcd key:

    spec:
  etcd:
    retentionPolicy:
      retentionType: RetentionNumber (1)
      retentionNumber:
        maxNumberOfBackups: 5 (2)
    1 The retention type. Defaults to RetentionNumber if unspecified.
    2 The maximum number of backups to retain. Adjust this value for your needs. Defaults to 15 backups if unspecified.

    A known issue causes the number of retained backups to be one greater than the configured value.

    For retention based on the file size of backups, use the following:

    spec:
  etcd:
    retentionPolicy:
      retentionType: RetentionSize
      retentionSize:
        maxSizeOfBackupsGb: 20 (1)
    1 The maximum file size of the retained backups in gigabytes. Adjust this value for your needs. Defaults to 10 GB if unspecified.

    A known issue causes the maximum size of retained backups to be up to 10 GB greater than the configured value.

  4. Create the cron job defined by the CRD by running the following command:

    $ oc create -f etcd-recurring-backup.yaml

  5. To find the created cron job, run the following command:

    $ oc get cronjob -n openshift-etcd