Is it valid to use --cluster-init with only one server?

[ChristianCiach]

The documentation isn't clear about this. Can I use the embedded etcd with only using one server (of course, without HA)? Is k3s server --cluster-init valid in this case?

Edit:

This doesn't look good:

$ k3s etcd-snapshot
FATA[2021-06-09T09:28:25.795674663-04:00] managed etcd database has not been initialized

[brandond]

Yes, you can run a single-node etcd cluster by passing --cluster-init.

Are you sure you've restarted the server with --cluster-init before attempting to take a snapshot?

[ChristianCiach]

Thank you! It's nice to have an official confirmation that this is actually supposed to work and does not only work by accident.

I've identified the cause why k3s etcd-snapshot didn't work for me before: I didn't run this command with sudo. Although I've installed K3s with write-kubeconfig-mode: '0644' (and kubectl-commands work fine without sudo), k3s etcd-snapshot insists to be called via sudo:

[vagrant@k3s-server-1 ~]$ kubectl get nodes
NAME           STATUS   ROLES                       AGE   VERSION
k3s-agent-1    Ready    <none>                      10m   v1.21.1+k3s1
k3s-server-1   Ready    control-plane,etcd,master   11m   v1.21.1+k3s1

[vagrant@k3s-server-1 ~]$ k3s etcd-snapshot
FATA[2021-06-11T11:21:33.427082412Z] managed etcd database has not been initialized 

[vagrant@k3s-server-1 ~]$ sudo k3s etcd-snapshot
INFO[2021-06-11T11:21:44.324976430Z] Managed etcd cluster bootstrap already complete and initialized 
W0611 11:21:44.336049    9282 warnings.go:70] apiextensions.k8s.io/v1beta1 CustomResourceDefinition is deprecated in v1.16+, unavailable in v1.22+; use apiextensions.k8s.io/v1 CustomResourceDefinition
W0611 11:21:44.343039    9282 warnings.go:70] apiextensions.k8s.io/v1beta1 CustomResourceDefinition is deprecated in v1.16+, unavailable in v1.22+; use apiextensions.k8s.io/v1 CustomResourceDefinition
W0611 11:21:44.346082    9282 warnings.go:70] apiextensions.k8s.io/v1beta1 CustomResourceDefinition is deprecated in v1.16+, unavailable in v1.22+; use apiextensions.k8s.io/v1 CustomResourceDefinition
INFO[2021-06-11T11:21:44.355481652Z] Saving etcd snapshot to /var/lib/rancher/k3s/server/db/snapshots/on-demand-k3s-server-1-1623410504 
{"level":"info","msg":"created temporary db file","path":"/var/lib/rancher/k3s/server/db/snapshots/on-demand-k3s-server-1-1623410504.part"}
{"level":"info","ts":"2021-06-11T11:21:44.358Z","caller":"clientv3/maintenance.go:200","msg":"opened snapshot stream; downloading"}
{"level":"info","msg":"fetching snapshot","endpoint":"https://127.0.0.1:2379"}
{"level":"info","ts":"2021-06-11T11:21:44.393Z","caller":"clientv3/maintenance.go:208","msg":"completed snapshot read; closing"}
{"level":"info","msg":"fetched snapshot","endpoint":"https://127.0.0.1:2379","size":"3.5 MB","took":"41.570489ms"}
{"level":"info","msg":"saved","path":"/var/lib/rancher/k3s/server/db/snapshots/on-demand-k3s-server-1-1623410504"}
INFO[2021-06-11T11:21:44.397475355Z] Saving current etcd snapshot set to k3s-etcd-snapshots ConfigMap 

Thanks!