NSS altfiles module

This is a NSS module which can read user information from files in the same format as /etc/passwd and /etc/group stored in an alternate location (/lib by default).

As of version 2.19.0, the module supports also files mimicking other files from /etc, and which file types are supported can be selected at build time:

• /etc/rpc
• /etc/protocols
• /etc/hosts
• /etc/networks
• /etc/services
• /etc/shadow
• /etc/gshadow

Essentially, it is a tweaked copy of the sources for the NSS files module included with glibc2 (or eglibc in versions prior to 2.19.0).

Usage

List the module the /etc/nsswitch.conf configuration file. For example:

passwd: files altfiles
group:  files altfiles

# Other entries follow...

This will try to read files from /etc first, and under /lib (using the altfiles module). Modifications will be stored in the files under /etc (e.g. when using passwd to change an user passwords).

Building

The usual ./configure && make && make install dance will work. The configure script allows to change the install path and the path to the alternative data files:

./configure --prefix=/installdir/path --datadir=/var

To select which file types will be supported, use the --with-types=FOO flag:

./configure --with-types=pwd,grp,hosts

The example above would build an altfiles NSS module that will read user information from /var/passwd and /var/group, which is to be installed under /installdir/path/lib.

To ease the task of packagers, the DESTDIR variable can be passed to make:

make install DESTDIR=/tmp/fakerootdir

Version scheme

Version numbers follow the numbering of the eglibc releases, adding a local revision number: <eglibc version>.<revision>. For example version 2.13.0 would contain the source files from eglibc 2.13, and the base modifications to make it the altfiles module; version 2.15.3 would contain the source files from eglibc 2.15, and the base modifications plus three patches.

Starting from version 2.19.0, version numbers follow glibc2 versions, as eglibc is no longer developed because its changes were merged back into glibc2.

Git tags do also follow this versioning.

Licensing

As eglibc and glibc are distributed under the terms of the LGPL 2.1, the same applies to the extra bits needed to make nss_altfiles work.

See the COPYING file in the source directory for the full text of the license.