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Backup and Restore etcd in Kubernetes Cluster for CKA v1.19

 1 year ago
source link: https://brandonwillmott.com/2020/09/03/backup-and-restore-etcd-in-kubernetes-cluster-for-cka-v1-19/
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The final module of the Cluster Architecture, Installation, and Configuration is Implement etcd backup and restore. Let’s quickly perform the actions we need to complete this step for the exam.

Perform a Backup of etcd

While it’s still early and details of the CKA v1.19 environment aren’t known yet, I’m anticipating a small change to how etcd backup and restore is performed. If you’ve been preparing for the CKA before the September 2020 change to Kubernetes v1.19, you may know be familiar with the environment variable export ETCDCTL_API=3 to ensure you’re using version 3 of etcd’s API, which has the backup and restore capability. However, Kubernetes v1.19 ships with etcd 3.4.9 and in etcd 3.4.x, the default API version is 3 so this process is no longer necessary! If etcdctl version returns a version lower than 3.4.x, you will still need to set the API version to 3 for performing backup and restore operations.

Get The Info You Need First

When you type the etcd backup command, you’re going to need to specify the location of a few certificates and a key. Let’s grab that really quick! Get the name of our etcd pod:

kubectl get pods -A

Get the details of our etcd pod:

kubectl describe pods etcd-controlplane -n kube-system

The output that we’re interested in is under the Command section. You will need to copy the locations of:

  • cert-file
  • key-file
  • trusted-ca-file
  • listen-client-urls
Command: 
etcd
--advertise-client-urls=https://172.17.0.54:2379
--cert-file=/etc/kubernetes/pki/etcd/server.crt
--client-cert-auth=true --data-dir=/var/lib/etcd
--initial-advertise-peer-urls=https://172.17.0.54:2380
--initial-cluster=master=https://172.17.0.54:2380
--key-file=/etc/kubernetes/pki/etcd/server.key
--listen-client-urls=https://127.0.0.1:2379,https://172.17.0.54:2379
--listen-metrics-urls=http://127.0.0.1:2381
--listen-peer-urls=https://172.17.0.54:2380
--name=master
--peer-cert-file=/etc/kubernetes/pki/etcd/peer.crt
--peer-client-cert-auth=true
--peer-key-file=/etc/kubernetes/pki/etcd/peer.key
--peer-trusted-ca-file=/etc/kubernetes/pki/etcd/ca.crt
--snapshot-count=10000
--trusted-ca-file=/etc/kubernetes/pki/etcd/ca.crt

Now here’s the fun part: the names of the options that etcd uses isn’t the same that etcdctl uses for the backup. They’re close enough to match up. Here’s how they map:

etcd optionsetcdctl options–cert-file–cert–key-file–key–trusted-ca-file–cacert–listen-client-urls–endpoints

Your backup command should look like this:

etcdctl snapshot save etcd.db \
--cacert=/etc/kubernetes/pki/etcd/ca.crt \
--cert=/etc/kubernetes/pki/etcd/server.crt \
--endpoints=https://127.0.0.1:2379 \
--key=/etc/kubernetes/pki/etcd/server.key

Output:

{"level":"info","ts":1603021662.1152575,"caller":"snapshot/v3_snapshot.go:119","msg":"created temporary db file","path":"etcd.db.part"}{"level":"info","ts":"2020-10-18T11:47:42.129Z","caller":"clientv3/maintenance.go:200","msg":"opened snapshot stream; downloading"}
{"level":"info","ts":1603021662.1302097,"caller":"snapshot/v3_snapshot.go:127","msg":"fetching snapshot","endpoint":"https://127.0.0.1:2379"}
{"level":"info","ts":"2020-10-18T11:47:42.173Z","caller":"clientv3/maintenance.go:208","msg":"completed snapshot read; closing"}
{"level":"info","ts":1603021662.198739,"caller":"snapshot/v3_snapshot.go:142","msg":"fetched snapshot","endpoint":"https://127.0.0.1:2379","size":"1.8 MB","took":0.083223978}
{"level":"info","ts":1603021662.199425,"caller":"snapshot/v3_snapshot.go:152","msg":"saved","path":"etcd.db"}
Snapshot saved at etcd.db

That’s it! The etcd database is backed up and we’re ready to restore!

Perform a Restore of etcd

With a restore, we’re going to specify those same 4 parameters from the backup operation but add a few more that are needed to initialize the restore as a new etcd store:

etcdctl snapshot restore etcd.db \
--endpoints=https://127.0.0.1:2379 \
--cacert=/etc/kubernetes/pki/etcd/ca.crt \
--cert=/etc/kubernetes/pki/etcd/server.crt \
--key=/etc/kubernetes/pki/etcd/server.key \
--name=controlplane \
--data-dir /var/lib/etcd-from-backup \
--initial-cluster=controlplane=https://127.0.0.1:2380 \
--initial-cluster-token=etcd-cluster-1 \
--initial-advertise-peer-urls=https://127.0.0.1:2380 \

What are these extra parameters doing?

  • Giving the etcd cluster a new name
  • Restoring the etcd snapshot to the /var/lib/etcd-from-backup directory
  • Re-initializing the etcd cluster token since we are creating a new cluster
  • Specifying the IP:Port for etcd-to-etcd communication

Output:

{"level":"info","ts":1603021679.8156757,"caller":"snapshot/v3_snapshot.go:296","msg":"restoring snapshot","path":"etcd.db","wal-dir":"/var/lib/etcd-from-backup/member/wal","data-dir":"/var/lib/etcd-from-backup","snap-dir":"/var/lib/etcd-from-backup/member/snap"}
{"level":"info","ts":1603021679.8793259,"caller":"membership/cluster.go:392","msg":"added member","cluster-id":"7581d6eb2d25405b","local-member-id":"0","added-peer-id":"e92d66acd89ecf29","added-peer-peer-urls":["https://127.0.0.1:2380"]}
{"level":"info","ts":1603021679.9166896,"caller":"snapshot/v3_snapshot.go:309","msg":"restored snapshot","path":"etcd.db","wal-dir":"/var/lib/etcd-from-backup/member/wal","data-dir":"/var/lib/etcd-from-backup","snap-dir":"/var/lib/etcd-from-backup/member/snap"}

For the CKA exam, this is all that’s necessary to complete the task! However, in production you wouldn’t want to stop here since this process doesn’t modify the existing etcd pod in anyway. The restore process will expand the snapshot into the directory specified and make some changes to the data to represent the new name and cluster token but that’s it!

In production, you would modify the etcd pod’s manifest in /etc/kubernetes/manifests/etcd.yaml to utilize the new data directory and the initial cluster token. Upon saving the file, the etcd pod will be destroyed and recreated and after a minute or so, the pod will be running and ready. You will also be able to check it by viewing the logs with kubectl logs <etcd-pod-name>.


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