etcd is the key-value store for OKD, 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 OKD 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 after you upgrade your cluster. This 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 OKD 4.y.z cluster must use an etcd backup that was taken from 4.y.z.

Back up your cluster’s etcd data by performing a single invocation of the backup script on a control plane host (also known as the master 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 (also known as the master host). Do not take a backup from each control plane host in the cluster.

  • 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.

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

    $ oc debug node/<node_name>
  2. Change your root directory to /host:

    sh-4.2# chroot /host
  3. If the cluster-wide proxy is enabled, be sure that you have exported the NO_PROXY, HTTP_PROXY, and HTTPS_PROXY environment variables.

  4. Run the cluster-backup.sh script 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
    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":""}
    {"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":"","size":"114 MB","took":1.584090459}
    Snapshot saved at /home/core/assets/backup/snapshot_2021-06-25_190035.db
    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.