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28.1 NSS Basics

The basic idea is to put the implementation of the different services offered to access the databases in separate modules. This has some advantages:

  1. Contributors can add new services without adding them to GNU C Library.
  2. The modules can be updated separately.
  3. The C library image is smaller.

To fulfill the first goal above the ABI of the modules will be described below. For getting the implementation of a new service right it is important to understand how the functions in the modules get called. They are in no way designed to be used by the programmer directly. Instead the programmer should only use the documented and standardized functions to access the databases.

The databases available in the NSS are

aliases
Mail aliases
ethers
Ethernet numbers,
group
Groups of users, see Group Database.
hosts
Host names and numbers, see Host Names.
netgroup
Network wide list of host and users, see Netgroup Database.
networks
Network names and numbers, see Networks Database.
protocols
Network protocols, see Protocols Database.
passwd
User passwords, see User Database.
rpc
Remote procedure call names and numbers,
services
Network services, see Services Database.
shadow
Shadow user passwords,

There will be some more added later (automount, bootparams, netmasks, and publickey).