# nss-myhostname 0.3

Copyright 2005-2011 Lennart Poettering <mzzlubfganzr (at) 0pointer (dot) de>

## License

This program is free software; you can redistribute it and/or modify it under the terms of the GNU Lesser General Public License as published by the Free Software Foundation, either version 2.1 of the License, or (at your option) any later version.

This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more details.

## News

Mon May 9 2011:

Version 0.3 released. Changes include: Always return locally configured IP addresses first, use 127.0.0.2/::1 only as fallback if no addresses are configured.

Mon Oct 27 2008:

Version 0.2 released. Changes include: Update for IPv6 and newest glibc NSS interfaces

Sat Nov 19 2005:

Version 0.1 released. Initial release.

## Overview

`nss-myhostname` is a plugin for the GNU Name Service Switch (NSS) functionality of the GNU C Library (`glibc`) providing host name resolution for the locally configured system hostname as returned by `gethostname(2)`. Various software relies on an always resolvable local host name. When using dynamic hostnames this is usually achieved by patching `/etc/hosts` at the same time as changing the host name. This however is not ideal since it requires a writable `/etc` file system and is fragile because the file might be edited by the administrator at the same time. `nss-myhostname` simply returns all locally configure public IP addresses, or -- if none are configured -- the IPv4 address `127.0.0.2` (wich is on the local loopback) and the IPv6 address `::1` (which is the local host) for whatever system hostname is configured locally. Patching `/etc/hosts` is thus no longer necessary.

## Current Status

It works!

## Documentation

After compiling and installing `nss-myhostname` you'll find a new NSS modules in `/lib`:

- `libnss_myhostname.so.2`

To activate the NSS modules you have to edit `/etc/nsswitch.conf` and add `myhostname` to the line starting with "`hosts:`". On Debian this looks like this:

    # /etc/nsswitch.conf

    passwd:         compat
    group:          compat
    shadow:         compat

    hosts:          files dns myhostname
    networks:       files

    protocols:      db files
    services:       db files
    ethers:         db files
    rpc:            db files

    netgroup:       nis

That's it. You should now always be able to resolve your local system hostname. For a quick check use `glibc`'s `getent` tool:

    $ getent ahosts `hostname`
    ::1             STREAM omega
    ::1             DGRAM
    ::1             RAW
    127.0.0.2       STREAM
    127.0.0.2       DGRAM
    127.0.0.2       RAW

In this case the local host name is omega.

It is recommended to put `myhostname` last in the `nsswitch.conf` line to make sure that this mapping is only used as fallback, and any DNS or `/etc/hosts` based mapping takes precedence.

## Requirements

`nss-myhostname` uses NSS interfaces that are specific to modern `glibc`'s.

`nss-myhostname` was developed and tested on Fedora 15 from May 2011, it should work on most other Linux distributions since it uses GNU autoconf and GNU libtool for source code configuration and shared library management.

## Installation

As this package is made with the GNU autotools you should run `./configure` inside the distribution directory for configuring the source tree. After that you should run `make` for compilation and `make install` (as root) for installation of `nss-myhostname`.

## Acknowledgements

None so far.

## Download

The newest release is always available from http://0pointer.de/lennart/projects/nss-myhostname/

The current release is 0.3

Get `nss-myhostname`'s development sources from the GIT repository (gitweb):

    git clone git://git.0pointer.de/nss-myhostname