Configuration

The full source of truth for every flag is server/embed/config.go (Config struct + Validate/parse). The companion etcd.conf.yml.sample at the repo root demonstrates every option in YAML form.

Where to look

• server/embed/config.go — the Config struct and all defaults (DefaultName, DefaultMaxSnapshots, ...).
• server/embed/config_logging.go, config_tracing.go — logging and tracing parsing.
• server/etcdmain/help.go — the long-form --help text.
• etcd.conf.yml.sample — annotated YAML.
• server/embed/etcd.go — embed.StartEtcd(cfg) validates and starts.
• server/etcdmain/grpc_proxy.go and gateway.go — separate flag sets for those modes.

Headline flags (member mode)

Identity and bootstrap

Flag	Default	Notes
--name	default	Human name for this member
--data-dir	${name}.etcd	Where WAL + bbolt + snapshots live
--wal-dir	<data-dir>/member/wal	Override WAL location for performance
--initial-cluster	empty	Static topology spec
--initial-cluster-state	new	new or existing
--initial-cluster-token	etcd-cluster	Disambiguates clusters with overlapping member IDs
--discovery	empty	Legacy v2 discovery URL
--discovery-srv	empty	DNS SRV-based discovery domain
--discovery-fallback	proxy	exit or proxy if discovery fails

Networking

Flag	Default	Notes
--listen-peer-urls	http://localhost:2380	Peer-to-peer transport URLs
--listen-client-urls	http://localhost:2379	Client gRPC + REST URLs
--initial-advertise-peer-urls	matches --listen-peer-urls	Advertised to peers
--advertise-client-urls	matches --listen-client-urls	Advertised to clients
--max-request-bytes	~1.5 MiB	Server-side request size cap
--grpc-keepalive-min-time / -interval / -timeout	5s / 2h / 20s	gRPC keepalive
--max-concurrent-streams	unlimited	gRPC MaxConcurrentStreams

Storage

Flag	Default	Notes
--quota-backend-bytes	0 (= 2 GiB)	NOSPACE alarm threshold
--snapshot-count	10000	Raft snapshot every N committed entries
--max-snapshots	5	Snapshot file retention
--max-wals	5	WAL file retention
--auto-compaction-mode	periodic	periodic or revision
--auto-compaction-retention	0 (off)	Duration or revision count
--backend-batch-interval	100 ms	bbolt commit cadence
--backend-batch-limit	10000	Ops per commit
--backend-bbolt-freelist-type	array	bbolt freelist type

TLS

Flag	Default	Notes
--cert-file, --key-file	empty	Client-facing TLS material
--client-cert-auth	false	Require client cert
--trusted-ca-file	empty	CA used to validate client certs
--auto-tls	false	Self-sign on first start (dev only)
--peer-cert-file, --peer-key-file, --peer-trusted-ca-file, --peer-client-cert-auth, --peer-auto-tls	empty/false	Peer counterparts
--cipher-suites	empty	Allowed cipher suites
--tls-min-version	TLS1.2	Floor TLS version

Auth / RBAC

Flag	Default	Notes
--auth-token	simple	simple,ttl=... or jwt,pub-key=...,priv-key=...,sign-method=...,ttl=...

Logging

Flag	Default	Notes
--logger	zap	Only zap is supported in current versions
--log-level	info	One of debug, info, warn, error, dpanic, panic, fatal
--log-outputs	default	Comma-separated; values include stderr, stdout, file paths, systemd/journal
--log-format	json	json or console
--log-rotation-config-json	empty	Lumberjack-style rotation

Tracing

Flag	Default	Notes
--experimental-enable-distributed-tracing	false	Toggle OTLP exporter
--experimental-distributed-tracing-address	localhost:4317	Collector endpoint
--experimental-distributed-tracing-service-name	etcd	Resource attribute
--experimental-distributed-tracing-sampling-rate-per-million	0	0 = follow parent decision

Feature gates

Flag	Default	Notes
--feature-gates	empty	Foo=true,Bar=false overrides; gates declared in server/features/etcd_features.go

Debug / health

Flag	Default	Notes
--enable-pprof	false	Mount /debug/pprof/* on the client port
--metrics	basic	basic or extensive
--strict-reconfig-check	true	Reject reconfigs that lose quorum

Environment variables

Most flags also accept an ETCD_<FLAG_UPPERCASE_WITH_UNDERSCORES> env var. The translation is implemented in server/etcdmain/config.go::parse. Where flags conflict, the YAML config file takes precedence over flags, which take precedence over env vars; the actual order is documented in --help.

YAML config file

Use --config-file=etcd.conf.yml. The file is parsed by sigs.k8s.io/yaml into the same Config struct.

A documented sample sits at etcd.conf.yml.sample.

Gateway and grpc-proxy modes

These have their own flag sets (smaller, no storage). See server/etcdmain/gateway.go and server/etcdmain/grpc_proxy.go. Flags are documented in server/etcdmain/help.go.