What is etcd in Kubernetes?

Question

Accepted Answer

**etcd** — distributed key-value store, the single source of truth for cluster state.

**Features:**
- Consistent and highly available.
- Watch support for changes.
- Transaction support.

```bash
# Check etcd health
ETCDCTL_API=3 etcdctl endpoint health \
  --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

# List all keys
ETCDCTL_API=3 etcdctl get / --prefix --keys-only

# Backup etcd
ETCDCTL_API=3 etcdctl snapshot save /backup/etcd-snapshot.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
```

**Best practices:**
- Regular backups.
- Odd number of nodes (3 or 5).
- Separate from application workloads.

DevOps: What is etcd in Kubernetes?