Persist node identity and state

This page has not been written. By default an EdgeVPN node generates a fresh libp2p key on every start, so its peer ID changes on every restart. Under --ownership enforce (the default) that orphans everything the node had announced. The flags that change this are documented only by their one-line --help text.

What is missing, and where the source is:

• --privkey-cache (env EDGEVPNPRIVKEYCACHE, off by default, marked experimental) and --privkey-cache-dir (env EDGEVPNPRIVKEYCACHEDIR, defaulting to $HOME/.edgevpn). The implementation is in cmd/util.go: it reads or generates <dir>/privkey, writing the directory 0700 and the file 0600. The comment above it explains why it is not enabled automatically — the default directory is per-user, so two co-located EdgeVPN processes sharing it would boot with the same peer ID. Each node needs its own directory.
• The interaction with ownership. cmd/util.go emits a warning when ownership enforcement is on and the identity is ephemeral, because the node’s entries are reclaimed after the liveness TTL on every restart. See ledger ownership.
• --ledger-state (env EDGEVPNLEDGERSTATE) is a different thing that gets confused with the above: it points the ledger at a DiskStore (pkg/blockchain/store_disk.go) instead of the default in-memory store. It persists the block chain, not the identity.
• Backup, rotation and revocation of a cached key: not addressed anywhere.

Contributions welcome — see contributing.