NSS means Name Service Switch. There is a good description of NSS here: http://www.gnu.org/software/libc/manual/html_node/Name-Service-Switch.html

What is important to know about NSS from an application packaging perspective is:

  • There are functions such as:
    • translation a uid to a user name and back
    • translation a gid to a group name and back
    • translation a hostname to an IP addresses and back
    • and more
  • The behavior of those functions is configured in the NSS Configuration File
  • Depending on the configuration in /etc/nsswitch.conf different NSS shared libraries can be loaded and used by an application, like libnss_files.so.2, libnss_dns.so.2, etc.
  • Those libraries aren't detected by ldd, so if the application uses them the --with-nss option should be specified.