# Recovering a partition from Longhorn Backup volume

## Pull the volume in the longhorn ui
Under backups, choose which ones to restore (data and wal). Be sure that the replica count is 1, 
the ReadWrite mode is ReadWriteOne. This should match what you had for the Pg volumes.

Get the volumes onto the same node. You may need to attach them, change the replica count, 
then delete off of the undesired node.

## Swap the Volume under the PVC
Put CNPG into hibernate mode and wait for the database nodes to clear.

```yaml
cluster
metadata:
  name: postgres-shared
  namespace: postgresql-system
  annotations:
    # 🔑 CRITICAL: Hibernation prevents startup and data erasure
    cnpg.io/hibernation: "on"
spec:
  instances: 1 # it's way easier to start with one instance

  # put the cluster into single node configuration
  minSyncReplicas: 0
  maxSyncReplicas: 0
```

If you haven't deleted the db cluster you should be able to use the same volume names as the preivous primary.
If you did, then you'll use postgresql-shared-1 or whatever your naming scheme is. But wait to make them
until AFTER the initdb runs the first time. If you are starting over, you'll have to set the 
annotation for `lastGeneratedNode` to 0. 
`kubectl patch clusters.postgresql.cnpg.io mydb --type=merge --subresource status --patch 'status: {latestGeneratedNode: 0}'` so that it'll create the first instance.
You'll also want to use a new PVC so that initdb clears out the data and then swap in your volume into that one.


Once you're past this stage, put it back into hibernation mode.

(why did I delete the files???)

Anyway, you need to swap the volume out from under the PVC that you're going to use.
You'll make a new pvc and set the (target?) uuid that identifies the volume to a new value.
I think this comes from longhorn. Make sure that the volume labels match the names of your recovery volumes.

Then you'll have to make sure that your PVCs are annotated with the same annotations on your previous PVCs 
since CNPG puts it's own annotations on them. It'll look like the below from https://github.com/cloudnative-pg/cloudnative-pg/issues/5235. Make sure that versions and everything else matches. You need these otherwise the operator won't find a volume to use.
```yaml
  annotations:
    cnpg.io/nodeSerial: "1"
    cnpg.io/operatorVersion: 1.24.0
    cnpg.io/pvcStatus: ready
    pv.kubernetes.io/bind-completed: "yes"
    pv.kubernetes.io/bound-by-controller: "yes"
    volume.beta.kubernetes.io/storage-provisioner: driver.longhorn.io
    volume.kubernetes.io/storage-provisioner: driver.longhorn.io
  finalizers:
  - kubernetes.io/pvc-protection
  labels:
    cnpg.io/cluster: mydb
    cnpg.io/instanceName: mydb-1
    cnpg.io/instanceRole: primary
    cnpg.io/pvcRole: PG_DATA
    role: primary
  name: mydb-1
  namespace: mydb
  ownerReferences:
  - apiVersion: postgresql.cnpg.io/v1
    controller: true
    kind: Cluster
    name: mydb
    uid: f1111111-111a-111f-111d-11111111111f
```

### Go out of hibernation mode.
You should see your pod come up and be functional, without an initdb pod. Check it.
After a while, scale it back up.