# WHATPORT(4045)

## NAME

port 4045 — NFS lock manager (lockd / NLM) — The NFS Network Lock Manager — a file server's advisory locking service, sitting next to NFS itself.

Protocol: TCP/UDP  
IANA registry

## DESCRIPTION

NLM is the RPC service that grants advisory file and record locks for NFSv2 and NFSv3, since those protocols are stateless and cannot track locks themselves. Solaris and its descendants fix lockd on port 4045 on both TCP and UDP, and Linux registers nlockmgr on a dynamic port unless an administrator pins it (for example via lockd.port in nfs.conf). IANA's own name for 4045 is npp, Network Paging Protocol, which you will essentially never see; the lock manager is what scanners find. NFSv4 folds locking into the main protocol, so a host showing 4045 is serving NFSv3 or older.

## EXPOSURE

**Do not expose.** It is an unauthenticated RPC service tied to a file server's guts, and the UDP side is spoofable — keep NFS and its lock manager on a trusted network.

## CHECK

```sh
rpcinfo -p TARGET | grep -E 'nlockmgr|lockd'
```

## SEE ALSO

- spec — [The Open Group — XNFS Version 3W, Chapter 10: Network Lock Manager Protocol](https://pubs.opengroup.org/onlinepubs/9629799/chap10.htm) (pubs.opengroup.org)
- iana — [IANA port registry — 4045 (npp)](https://www.iana.org/assignments/service-names-port-numbers/service-names-port-numbers.xhtml?search=4045) (iana.org)

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HTML: <https://whatport.net/4045/> · JSON: <https://whatport.net/4045.json> · full dataset: <https://whatport.net/ports.json>