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OpenShift etcd backup CronJob

This CronJob creates an POD which runs /usr/local/bin/cluster-backup.sh on a master-node to create the described backup. After finishing, it copies the files to an configured PV and expires old backups according to its configuration.

The OpenShift 4 backup generates 2 different files with the date when it is performed:

  • snapshot_2021-03-17_153108.db
  • static_kuberesources_2021-03-17_153108.tar.gz

The .db file is a snapshot of the etcd and the .tar.gz contains the static pods of the control plane (etcd, api server, controller manager and scheduler) with their respective certificates and private keys. Those files are put in an seperate directory on the PV per backup run.

Installation

Fist, create a namespace:

oc new-project etcd-backup

Since the container needs to be privileged, add the reqired RBAC rules:

oc create -f backup-rbac.yaml

Then create a configmap with the backup-script:

oc create configmap backup-script --from-file=backup.sh

Then adjust storage to your needs in backup-storage.yaml and deploy it. The example uses NFS but you can use any storage class you want.

oc create -f backup-storage.yaml

Configure the backup-script (for now only retention in days can be configured in the)

oc create -f backup-config.yaml

Then deploy, and configure the cronjob

# find image hash
toolsImage=$(oc adm release info --image-for=tools)

# If you run in a restricted network, you need to add registry-config:
toolsImage=$(oc adm release info --image-for=tools --registry-config=./pull-secret.json)

# deploy the cronjob
oc create -f backup-cronjob.yaml

# adjust the tools image
oc patch cronjob/etcd-backup -p "{\"spec\":{\"jobTemplate\":{\"spec\":{\"template\":{\"spec\":{\"containers\":[{\"image\":\"${toolsImage}\",\"name\":\"backup-etcd\"}]}}}}}}'"

Creating manual backup / testing

To test the backup, or create an manual backup, you can run a job:

backupName=$(date "+etcd-backup-manual-%F-%H-%M-%S")
oc create job --from=cronjob/etcd-backup ${backupName}

To see if everything works as it should, you can check the logs:

oc logs -l job-name=${backupName}

Then check on your Storage, if the files are there as excepted.

Configuration

Configuration can be changed in configmap backup-config:

oc edit -n etcd-backup cm/backup-config

The following options are used:

  • backup.subdir: Sub directory on PVC. If it not exists it will be created.
  • backup.dirname: Dirname of singe backup. This is a string which run trough date
  • backup.expiretype:
    • days: Keep backups newer than backup.keepdays.
    • count: Keep a number of backups. backup.keepcount is used to determine how much.
    • never: Dont expire backups, keep all of them.
  • backup.keepdays: Days to keep the backup. Only used if backup.expiretype is set to days
  • backup.keepcount: Number of backups to keep. Only used if backup.expiretype is set to count

Changing the schedule be done in the CronJob directly, with spec.schedule:

oc edit -n etcd-backup cronjob/etcd-backup

Default is 0 0 * * * which means the cronjob runs one time a day at midnight.

Update

After updating the cluster, it makes sense to update the image as well. To do this, execute the following:

# switch to project
oc project etcd-backup

# find image hash
toolsImage=$(oc adm release info --image-for=tools)

# If you run in a restricted network, you need to add registry-config:
toolsImage=$(oc adm release info --image-for=tools --registry-config=./pull-secret.json)

# adjust the tools image
oc patch cronjob/etcd-backup -p "{\"spec\":{\"jobTemplate\":{\"spec\":{\"template\":{\"spec\":{\"containers\":[{\"image\":\"${toolsImage}\",\"name\":\"backup-etcd\"}]}}}}}}'"

References