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29.1 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 the 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.

gshadow

Group passphrase hashes and related information.

hosts

Host names and numbers, see Host Names.

initgroups

Supplementary group access list.

netgroup

Network wide list of host and users, see Netgroup Database.

networks

Network names and numbers, see Networks Database.

passwd

User identities, see User Database.

protocols

Network protocols, see Protocols Database.

publickey

Public keys for Secure RPC.

rpc

Remote procedure call names and numbers.

services

Network services, see The Services Database.

shadow

User passphrase hashes and related information.

More databases may be added later.