vshn/k8up

= How to use Pre-Backup pods

Although K8up supports xref:how-tos/application-aware-backups.adoc[executing backup commands] in already running pods, there might be a need to start a specific Pod for the backup.
Like, what if the backup command you'd like to run isn't available in the running pod?
Or perhaps you want to backup something that's outside the Kubernetes cluster, like a managed cloud database?

That's the perfect use case for using PreBackup pods!
They're Pod definitions that live in your namespaces.
Once the Operator triggers a backup for that specific namespace, then it will loop through all these Pod definitions, execute them and clean them up after the backup finished.
They allow much more flexibility, as they support everything a normal Pod template does.
For instance, you are able to set Pod affinity, so that the PreBackup Pods are started on a specific node.

[source,yaml]
----
apiVersion: k8up.io/v1
kind: PreBackupPod
metadata:
  name: mysqldump
spec:
  backupCommand: sh -c 'mysqldump -u$USER -p$PW -h $DB_HOST --all-databases'
  pod:
    spec:
      containers:
        - env:
            - name: USER
              value: dumper
            - name: PW
              value: topsecret
            - name: DB_HOST
              value: mariadb.example.com
          image: mariadb
          command:
            - 'sleep'
            - 'infinity'
          imagePullPolicy: Always
          name: mysqldump

----

[TIP]
.Passing environment variables
====
If you want to pass environment variables to the `backupCommand`, then you'll have to wrap them in a shell. In the prebackup pod example above, that would look like this:

[source]
--
spec:
  backupCommand: /bin/bash -c 'mysqldump -uroot -p "${MARIADB_ROOT_PASSWORD}" --all-databases'" --overwrite
--

You can also add it to any pods that are running in the namespace:

[source,title="via kubectl"]
--
kubectl -n ${YOUR_NAMESPACE} annotate pods ${YOUR_POD_NAME} "k8up.io/backupcommand=/bin/bash -c 'mysqldump -uroot -p\"\${MARIADB_ROOT_PASSWORD}\" --all-databases'" --overwrite
--

[source,title="in the manifest"]
--
spec:
  serviceName: "mariadb"
  replicas: 1
  template:
    metadata:
      labels:
        app: mariadb
      annotations:
        k8up.io/backupcommand: /bin/bash -c 'mysqldump -uroot -p "${MARIADB_ROOT_PASSWORD}" --all-databases'
--
====


See <<references/object-specifications.adoc#_prebackup,PreBackup pods>> for detailed object specifications.