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Backing Up Persistent Volumes Using Stash

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Stephanie R.
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Learn how to use Stash to back up and restore persistent volumes on an OVHcloud Managed Kubernetes cluster.

Stash is an open-source tool to safely backup and restore, perform disaster recovery, and migrate Kubernetes persistent volumes.

We are using our Public Cloud’s Swift Object Storage with the Swift S3 API as the storage backend for Stash. Stash uses the S3 protocol to store the cluster backups on an S3-compatible object storage.

 

Before you begin

This tutorial presupposes that you already have a working OVHcloud Managed Kubernetes cluster and some basic knowledge of how to operate it. If you want to know more about those topics, please look at the OVHcloud Managed Kubernetes Service Quickstart.

You also need to have Helm installer on your workstation and your cluster, please refer to the How to Install Helm on OVHcloud Managed Kubernetes Service tutorial.

 

Create the S3 bucket for Stash

Stash needs an S3 bucket as a storage backend to store your cluster's data. In this section, you will create your S3 bucket on Swift.

Prepare your working environment

Before creating your S3 bucket you need to:

You should now have access to your OpenStack RC file, with a filename like <user_name>-openrc.sh, and the username and password for your OpenStack account.

 

Set the OpenStack environment variables

Set the environment variables by sourcing the OpenStack RC file:

source <user_name>-openrc.sh

The shell will ask you for your OpenStack password.

 

Create EC2 credentials

S3 tokens are different, you need two parameters (access and secret) to generate an S3 token.

These credentials will be safely stored in Keystone. To generate them with python-openstack client:

openstack ec2 credentials create

Save the access and secret parameters from the results.

Example result:

$ openstack ec2 credentials create
+------------+----------------------------------------------------------------------------------------------------------------------------+
| Field      | Value
+------------+----------------------------------------------------------------------------------------------------------------------------+
| access     | 5a4d8b8d88104123a862c527ede5a3d3
| links      | {u'self': u'https://auth.cloud.ovh.us/v3/users/d74d05ff121b44bea9216495e7f0df61/credentials/OS-EC2/5a4d8b8d88104123a862c527ede5a3d3'}
| project_id | 20e124b71be141299e111ec26b1892fa
| secret     | 925d5fcfcd9f436d8ffcb20548cc53a2
| trust_id   | None
| user_id    | d74d05ff121b44bea9216495e7f0df61
+------------+----------------------------------------------------------------------------------------------------------------------------+

 

Configure awscli client

Install the awscli client:

pip install awscli

Complete and write down the configuration for awscli into ~/aws/config:

[profile default]
aws_access_key_id = <access fetched in previous step>
aws_secret_access_key = <secret fetched in previous step>
region = <public cloud region in lower case>
endpoint_url = https://s3.<public cloud region without digit>.cloud.ovh.us
s3 =
  signature_version = s3v4
  addressing_style = virtual

 

Create an S3 bucket for Stash

Create a new bucket:

aws --profile default s3 mb s3://s3-stash

 

Create a Kubernetes Secret to store S3 credentials

To give Stash access to the S3 bucket, you need to put the credentials (the access_key and the secret_access_key) into a Kubernetes Secret.

To give Stash access to the S3 bucket, you need to put the credentials (the access_key and the secret_access_key) into a Kubernetes Secret.

kubectl create namespace nginx-example
echo -n '<access-key>' > AWS_ACCESS_KEY_ID
echo -n '<secret_access_key>' > AWS_SECRET_ACCESS_KEY
echo -n '<a_password>' > RESTIC_PASSWORD
kubectl create secret generic -n nginx-example s3-secret \
     --from-file=./RESTIC_PASSWORD \
    --from-file=./AWS_ACCESS_KEY_ID \
    --from-file=./AWS_SECRET_ACCESS_KEY

Example result:

$ kubectl create namespace nginx-example
namespace/nginx-example created

$ echo -n 'xxxxxxxxxxxxxxxxxxx' > AWS_ACCESS_KEY_ID

$ echo -n 'yyyyyyyyyyyyyyyyyyy' > AWS_SECRET_ACCESS_KEY

$ echo -n 'zzzzzzzzzzzzzzzzzzz' > RESTIC_PASSWORD

$ kubectl create secret generic -n nginx-example s3-secret \
>     --from-file=./RESTIC_PASSWORD \
>     --from-file=./AWS_ACCESS_KEY_ID \
>     --from-file=./AWS_SECRET_ACCESS_KEY
secret/s3-secret created

 

Install Stash

The easiest way to install Stash is via Helm, using the chart from AppsCode Charts Repository.

First of all, you need to get a license.

NOTE: If you want to use an enterprise edition, please follow this link instead.

You should receive your license by email. Save it as you will need it in the helm install command.

Begin by adding the repository:

helm repo add appscode https://charts.appscode.com/stable/
helm repo update

Then search the latest version of stash:

helm search repo appscode/stash --version v2021.11.24

And install it with the release name stash-operator:

helm install stash appscode/stash          \
  --version v2021.11.24                \
  --namespace kube-system                     \
  --set features.community=true               \
  --set-file global.license=<PATH_TO_YOUR_STASH_LICENSE>

Example result:

$ helm repo add appscode https://charts.appscode.com/stable/

"appscode" has been added to your repositories

$ helm repo update

Hang tight while we grab the latest from your chart repositories...
[...]
...Successfully got an update from the "appscode" chart repository
[...]
Update Complete. ⎈Happy Helming!⎈

$ helm search repo appscode/stash --version v2021.11.24

NAME                    CHART VERSION   APP VERSION DESCRIPTION
appscode/stash          v2021.11.24     v2021.11.24 Stash by AppsCode - Backup your Kubernetes nati...
appscode/stash-catalog  v2021.11.24     v2021.11.24 Stash Catalog by AppsCode - Catalog of Stash Ad...
appscode/stash-crds     v2021.11.24     v2021.11.24 Stash Custom Resource Definitions
appscode/stash-metrics  v2021.11.24     v2021.11.24 Stash State Metrics

$ helm install stash appscode/stash          \
  --version v2021.11.24                \
  --namespace kube-system                     \
  --set features.community=true               \
  --set-file global.license=stash-community-license-c187ab99-64a1-4f65-9871-7e5168f48e8f.txt
W1221 14:36:32.478119   35817 warnings.go:70] policy/v1beta1 PodSecurityPolicy is deprecated in v1.21+, unavailable in v1.25+
W1221 14:36:35.308665   35817 warnings.go:70] policy/v1beta1 PodSecurityPolicy is deprecated in v1.21+, unavailable in v1.25+
W1221 14:36:35.484798   35817 warnings.go:70] policy/v1beta1 PodSecurityPolicy is deprecated in v1.21+, unavailable in v1.25+
W1221 14:36:35.526044   35817 warnings.go:70] policy/v1beta1 PodSecurityPolicy is deprecated in v1.21+, unavailable in v1.25+
W1221 14:36:35.838301   35817 warnings.go:70] spec.template.spec.nodeSelector[beta.kubernetes.io/arch]: deprecated since v1.14; use "kubernetes.io/arch" instead
W1221 14:36:35.838468   35817 warnings.go:70] spec.template.spec.nodeSelector[beta.kubernetes.io/os]: deprecated since v1.14; use "kubernetes.io/os" instead
NAME: stash
LAST DEPLOYED: Tue Dec 21 14:36:31 2021
NAMESPACE: kube-system
STATUS: deployed
REVISION: 1
TEST SUITE: None
NOTES:
Get the Stash operator pods by running the following command:

  kubectl --namespace kube-system get pods

 

Verify installation

As suggested during the chart install, to check if Stash operator pods have started, we can run the suggested command and customize it to see only our stash Pod:

kubectl get pods -A -l app.kubernetes.io/name=stash-community

If everything is OK, you should get a stash-stash-community pod with a status Running.

kubectl get pods -A -l app.kubernetes.io/name=stash-community
NAMESPACE     NAME                                     READY   STATUS    RESTARTS   AGE
kube-system   stash-stash-community-84b7f84b7f-ctzv7   2/2     Running   0          35s

Now, to confirm CRD groups have been registered by the operator, run the following command:

kubectl get crd | grep stash

Example result:

$ kubectl get crd | grep stash

backupblueprints.stash.appscode.com                   2021-12-21T13:36:47Z
backupconfigurations.stash.appscode.com               2021-12-21T13:36:46Z
backupsessions.stash.appscode.com                     2021-12-21T13:36:46Z
functions.stash.appscode.com                          2021-12-21T13:24:18Z
recoveries.stash.appscode.com                         2021-12-21T13:36:46Z
repositories.stash.appscode.com                       2021-12-21T13:36:46Z
restics.stash.appscode.com                            2021-12-21T13:36:46Z
restorebatches.stash.appscode.com                     2021-12-21T13:36:48Z
restoresessions.stash.appscode.com                    2021-12-21T13:36:47Z
tasks.stash.appscode.com                              2021-12-21T13:24:18Z

 

Install Stash kubectl plugin

Stash provides a CLI using kubectl plugin to work with the stash Objects quickly. Download pre-built binaries from stashed/cli Github release and put the binary to some directory in your PATH.

 

Volume Snapshot with Stash

A detailed explanation of Volume Snapshot with Stash is available in the official documentation.

In Kubernetes, a Volume Snapshot represents a snapshot of a volume on a storage system. It was introduced as an Alpha feature in Kubernetes v1.12 and has been promoted to a Beta feature in Kubernetes 1.17.

In order to support VolumeSnapshot, your PersistentVolumes need to use a StorageClass with a CSI driver that supports the feature. Currently, OVHcloud Managed Kubernetes cluster propose you two of these: StorageClasses, csi-cinder-classic, and csi-cinder-high-speed.

You also need a compatible VolumeSnapshotClass - in our case, csi-cinder-snapclass.

 

An example: Nginx server with persistent logs

For this example, we will use a small Nginx web server with a PersistentVolume to store the access logs.

Copy the following description to a nginx-example.yml file:

---
apiVersion: v1
kind: Namespace
metadata:
  name: nginx-example
  labels:
    app: nginx

---
kind: PersistentVolumeClaim
apiVersion: v1
metadata:
  name: nginx-logs
  namespace: nginx-example
  labels:
    app: nginx
spec:
  storageClassName: csi-cinder-high-speed
  accessModes:
    - ReadWriteOnce
  resources:
    requests:
      storage: 50Mi

---
apiVersion: apps/v1
kind: Deployment
metadata:
  name: nginx-deployment
  namespace: nginx-example
spec:
  strategy:
    type: Recreate
  replicas: 1
  selector:
    matchLabels:
      app: nginx
  template:
    metadata:
      labels:
        app: nginx
    spec:
      volumes:
        - name: nginx-logs
          persistentVolumeClaim:
            claimName: nginx-logs
      containers:
        - image: nginx:1.7.9
          name: nginx
          ports:
            - containerPort: 80
          volumeMounts:
            - mountPath: "/var/log/nginx"
              name: nginx-logs
              readOnly: false
---
apiVersion: v1
kind: Service
metadata:
  labels:
    app: nginx
  name: nginx-service
  namespace: nginx-example
spec:
  ports:
    - port: 80
      targetPort: 80
  selector:
    app: nginx
  type: LoadBalancer

And apply it to your cluster:

kubectl apply -f nginx-example.yml

If you look attentively to the deployment part of this manifest, you will see that we have defined a .spec.strategy.type. It specifies the strategy used to replace old Pods by new ones, and we have set it to Recreate, so all existing Pods are killed before new ones are created.

We do so as the Storage Class we are using, csi-cinder-high-speed, only supports a ReadWriteOnce, so we can only have one pod writing on the Persistent Volume at any given time.

We can check if the Pod is running:

kubectl get pod -n nginx-example

Wait until you get an external IP:

kubectl -n nginx-example get svc nginx-service -w

And do some calls to the URL to generate some access logs:

curl -I <EXTERNAL_IP>

Example results:

$ kubectl apply -f nginx-example.yml

namespace/nginx-example created
persistentvolumeclaim/nginx-logs created
deployment.apps/nginx-deployment created
service/nginx-service created

$ kubectl get pod -n nginx-example
NAME                                READY   STATUS    RESTARTS   AGE
nginx-deployment-766444c4d9-cxd2p   1/1     Running   0          32s

$ kubectl -n nginx-example get svc nginx-service -w

NAME            TYPE           CLUSTER-IP    EXTERNAL-IP   PORT(S)        AGE
nginx-service   LoadBalancer   10.3.39.164   <pending>     80:31734/TCP   49s
nginx-service   LoadBalancer   10.3.39.164   51.210.210.247   80:31734/TCP   3m

$ curl -I 51.210.210.247
HTTP/1.1 200 OK
Server: nginx/1.7.9
Date: Tue, 21 Dec 2021 14:16:20 GMT
Content-Type: text/html
Content-Length: 612
Last-Modified: Tue, 23 Dec 2014 16:25:09 GMT
Connection: keep-alive
ETag: "54999765-264"
Accept-Ranges: bytes

$ curl -I 51.210.210.247
HTTP/1.1 200 OK
Server: nginx/1.7.9
Date: Tue, 21 Dec 2021 14:16:31 GMT
Content-Type: text/html
Content-Length: 612
Last-Modified: Tue, 23 Dec 2014 16:25:09 GMT
Connection: keep-alive
ETag: "54999765-264"
Accept-Ranges: bytes

 

Verify the logs

Now we need to connect to the pod to read the log file and verify that our logs are written.

First, get the name of the Nginx running pod:

kubectl -n nginx-example get pods

And then connect to it and see your access logs:

kubectl -n nginx-example exec <POD_NAME> -c nginx -- cat /var/log/nginx/access.log

Example results:

$ kubectl -n nginx-example get pods

NAME                                READY   STATUS    RESTARTS   AGE
nginx-deployment-766444c4d9-cxd2p   1/1     Running   0          28m

$ kubectl -n nginx-example exec nginx-deployment-766444c4d9-cxd2p -c nginx -- cat /var/log/nginx/access.log
10.2.2.0 - - [21/Dec/2021:14:16:20 +0000] "HEAD / HTTP/1.1" 200 0 "-" "curl/7.64.1" "-"
10.2.0.0 - - [21/Dec/2021:14:16:31 +0000] "HEAD / HTTP/1.1" 200 0 "-" "curl/7.64.1" "-"

 

Create a Repository

A Repository is a Kubernetes CustomResourceDefinition (CRD) which represents backend information in a Kubernetes native way. You have to create a Repository object for each backup target. A backup target can be a workload, database or a PV/PVC.

To create a Repository CRD, you have to provide the storage secret that we have created earlier in spec.backend.storageSecretName field. You will also need to define spec.backend.s3.prefix, to choose the folder inside the backend where the backed up snapshots will be stored.

Create a repository.yaml file, replacing <public cloud region> with the region, without digits and in lowercase (e.g., us-east-va-1):

apiVersion: stash.appscode.com/v1alpha1
kind: Repository
metadata:
  name: s3-repo
  namespace: nginx-example
spec:
  backend:
    s3:
      endpoint: s3.<public cloud region>.cloud.ovh.us
      bucket: s3-stash
      region: <public cloud region>
      prefix: /backup/nginx-demo
    storageSecretName: s3-secret

And apply it to your Kubernetes cluster:

kubectl apply -f repository.yml

Example result:

$ kubectl apply -f repository.yaml
repository.stash.appscode.com/s3-repo created

 

Create a BackupConfiguration

A BackupConfiguration is a Kubernetes CustomResourceDefinition (CRD) which specifies the backup target, parameters (schedule, retention policy, etc.), and a Repository object that holds snapshot storage information in a Kubernetes-native way.

You have to create a BackupConfiguration object for each backup target. A backup target can be a workload, database, or a PV/PVC.

To back up our PV we will need to create a backup-configuration.yaml file, where we describe the Persistent Volumes we want to back up, the repository we intend to use and the backing up schedule (in crontab format):

apiVersion: stash.appscode.com/v1beta1
kind: BackupConfiguration
metadata:
  name: nginx-backup
  namespace: nginx-example
spec:
  repository:
    name: s3-repo
  schedule: "*/5 * * * *"
  target:
    ref:
      apiVersion: apps/v1
      kind: Deployment
      name: nginx-deployment
    volumeMounts:
      - name: nginx-logs
        mountPath: /var/log/nginx
    paths:
      - /var/log/nginx
  retentionPolicy:
    name: "keep-last-5"
    keepLast: 5
    prune: true

And apply it to your Kubernetes cluster:

kubectl apply -f backup-configuration.yml

Example result:

$ kubectl apply -f backup-configuration.yaml
backupconfiguration.stash.appscode.com/nginx-backup created

 

Verify CronJob

If everything goes well, Stash will create a CronJob to take periodic snapshot of nginx-logs volume of the deployment with the schedule specified in spec.schedule field of BackupConfiguration CRD (a backup every five minutes).

Check that the CronJob has been created:

kubectl -n nginx-example get cronjob

Example result:

$ kubectl -n nginx-example get cronjob
NAME                        SCHEDULE      SUSPEND   ACTIVE   LAST SCHEDULE   AGE
stash-backup-nginx-backup   */5 * * * *   False     0        33s             3m36s

 

Wait for BackupSession

The stash-backup-nginx-backup CronJob will trigger a backup on each schedule by creating a BackupSession CRD.

Wait for the next backup schedule. Run the following command to watch BackupSession CRD:

kubectl -n nginx-example get backupsession

Example result:

$ kubectl -n nginx-example get backupsessions
NAME                      INVOKER-TYPE          INVOKER-NAME   PHASE       AGE
nginx-backup-1586938564   BackupConfiguration   nginx-backup   Succeeded   77s

We can see above that the backup session has succeeded. Now, we are going to verify that the VolumeSnapshot has been created and the snapshots has been stored in the respective backend.

 

Verifying Volume Snapshots in OVHcloud Cloud Manager

The snapshots are visible in the OVHcloud Control Panel. To see them, go to Object Storage section, where you will find the S3 bucket you have created. By clicking on the bucket you will see the list of objects, including all the snapshots beginning with the /backup/demo/deployment/stash-demo we had defined in the Repository:

stash1.png

 

Restore PVC from VolumeSnapshot

This section will show you how to restore the PVCs from the snapshots we have taken in the previous section.

Stop Snapshotting

Before restoring we need to pause the BackupConfiguration to prevent any snapshotting during the restore process. With the BackupConfiguration, Stash will stop taking any further backups for nginx-deployment.

kubectl -n nginx-example patch backupconfiguration  nginx-backup --type="merge" --patch='{"spec": {"paused": true}}'

After some moments, you can look at the nginx-backup status to see it paused:

kubectl -n nginx-example get backupconfiguration nginx-backup

Example results:

$ kubectl -n nginx-example patch backupconfiguration  nginx-backup --type=
"merge" --patch='{"spec": {"paused": true}}'
backupconfiguration.stash.appscode.com/nginx-backup patched

$ kubectl -n nginx-example get backupconfiguration nginx-backup
NAME           TASK   SCHEDULE      PAUSED   AGE
nginx-backup          */1 * * * *   true     7m18s

 

Simulate Disaster

Let’s simulate a disaster scenario, deleting all the files from the PVC:

kubectl -n nginx-example exec <POD_NAME> -c nginx -- rm /var/log/nginx/access.log

And verify that the file is deleted:

kubectl -n nginx-example exec <POD_NAME> -c nginx -- ls -al /var/log/nginx/

Example results:

$ kubectl -n nginx-example -c nginx exec nginx-deployment-766444c4d9-cxd2p  -- rm /var/log/nginx/access.log

$ kubectl -n nginx-example exec nginx-deployment-766444c4d9-cxd2p -c nginx -- ls -al /var/log/nginx/
total 32
drwxr-xr-x 3 root root  4096 Dec 21 13:42 .
drwxr-xr-x 1 root root  4096 Jan 27  2015 ..
-rw-r--r-- 1 root root  1369 Dec 21 14:15 error.log
drwx------ 2 root root 16384 Dec 21 13:42 lost+found

 

Create a RestoreSession

Now you need to create a RestoreSession CRD to restore the PVCs from the last snapshot.

A RestoreSession is a Kubernetes CustomResourceDefinition (CRD) which specifies a target to restore and the source of data that will be restored in a Kubernetes native way.

Create a restore-session.yaml file:

apiVersion: stash.appscode.com/v1beta1
kind: RestoreSession
metadata:
  name: nginx-restore
  namespace: nginx-example
spec:
  repository:
    name: s3-repo
  target: # target indicates where the recovered data will be stored
    ref:
      apiVersion: apps/v1
      kind: Deployment
      name: nginx-deployment
    volumeMounts:
      - name: nginx-logs
        mountPath: /var/log/nginx

And apply it to your cluster:

kubectl apply -f restore-session.yaml

And wait for the RestoreSession to succeed:

kubectl -n nginx-example get restoresession  nginx-restore

Example results:

$ kubectl apply -f ./examples/stash/restore-session.yaml
restoresession.stash.appscode.com/nginx-restore created

$ kubectl get restoresession -n nginx-example nginx-restore -w
NAME            REPOSITORY   PHASE       AGE
nginx-restore   s3-repo      Succeeded   50s

 

Verify the data is restored

Let's begin by getting the pod name:

kubectl -n nginx-example get pods

And then verify that the access.log file has been restored:

kubectl -n nginx-example exec <POD_NAME> -c nginx -- ls -al /var/log/nginx/
kubectl -n nginx-example exec <POD_NAME> -c nginx -- cat /var/log/nginx/access.log

Example results:

$ kubectl -n nginx-example get pods
NAME                                READY   STATUS    RESTARTS   AGE
nginx-deployment-766444c4d9-cxd2p   2/2     Running   0          31s

$ kubectl -n nginx-example exec nginx-deployment-766444c4d9-cxd2p -c nginx -- cat /var/log/nginx/access.log

10.2.2.0 - - [21/Dec/2021:14:16:20 +0000] "HEAD / HTTP/1.1" 200 0 "-" "curl/7.64.1" "-"
10.2.0.0 - - [21/Dec/2021:14:16:31 +0000] "HEAD / HTTP/1.1" 200 0 "-" "curl/7.64.1" "-"

$ kubectl -n nginx-example exec nginx-deployment-766444c4d9-cxd2p -c nginx -- ls -al /var/log/nginx/

total 32
drwxr-xr-x 3 root root  4096 Dec 21 13:42 .
drwxr-xr-x 1 root root  4096 Jan 27  2015 ..
-rw-r--r-- 1 root root  1686 Dec 21 15:03 access.log
-rw-r--r-- 1 root root  1369 Dec 21 14:55 error.log
drwx------ 2 root root 16384 Dec 21 14:55 lost+found

 

Cleaning up

To clean up your cluster, begin by deleting the nginx-example namespace:

kubectl delete namespace nginx-example

Then simply use Helm to delete your Stash release.

helm uninstall stash -n kube-system

Example results:

$ kubectl delete namespace nginx-example
namespace "nginx-example" deleted

$ helm uninstall stash -n kube-system
release "stash" uninstalled

 

Go further

For more information and tutorials, please see our other Managed Kubernetes support guides or explore the guides for other OVHcloud products and services.

If you need training or technical assistance to implement our solutions, contact your sales representative or click on this link to get a quote and ask our Professional Services experts for a custom analysis of your project.

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