etcd

etcd is a highly available, consistent key-value data store. The k8s control plane uses it to store API server data.

For direct interactions, etcd comes with the etcdctl CLI client. The client supports both the etcd API v2.x and v3.x, but each version uses a different data model and protocol¹ — a key written using v2 is NOT queryable via v3 — so it’s worth checking which API version etcdctl is currently using before interacting with the store. You can set the version with the ETCDCTL_API variable.

Footnotes

1. etcd API v2 used a REST interface, while v3 uses gRPC. ↩