---
name: "nfnl_osf"
section: "8"
platform: "linux"
package: "iptables"
version: "1:1.8.13-1"
release: "Arch Linux 2026-11-01"
platforms: ["linux"]
url: "https://new.carta.tech/nfnl_osf"
---

# nfnl\_osf(8)

OS fingerprint loader utility

## NAME

nfnl\_osf — OS fingerprint loader utility

## SYNOPSIS

**nfnl\_osf** **-f** *fingerprints* \[ **-d** \]

## DESCRIPTION

The **nfnl\_osf** utility allows one to load a set of operating system signatures into the kernel for later matching against using iptables' **osf** match.

## OPTIONS

- **-f** *fingerprints*

  Read signatures from file *fingerprints*.

- **-d**

  Instead of adding the signatures from *fingerprints* into the kernel, remove them.

## EXIT STATUS

Exit status is 0 if command succeeded, otherwise a negative return code indicates the type of error which happened:

- **-1**

  Illegal arguments passed, fingerprints file not readable or failure in netlink communication.

- **-ENOENT**

  Fingerprints file not specified.

- **-EINVAL**

  Netlink handle initialization failed or fingerprints file format invalid.

## FILES

An up to date set of operating system signatures can be downloaded from http://www.openbsd.org/cgi-bin/cvsweb/src/etc/pf.os .

## SEE ALSO

The description of **osf** match in [**iptables-extensions**(8)](/iptables-extensions/8.md) contains further information about the topic as well as example **nfnl\_osf** invocations.