Linux 2.6 - man page for nss (linux section 5)
|Linux & Unix Commands - Search Man Pages
NSS(5) Linux Programmer's Manual NSS(5)
nss - Name Service Switch configuration file
Each call to a function which retrieves data from a system database like the password or
group database is handled by the Name Service Switch implementation in the GNU C library.
The various services provided are implemented by independent modules, each of which natu-
rally varies widely from the other.
The default implementations coming with the GNU C library are by default conservative and
do not use unsafe data. This might be very costly in some situations, especially when the
databases are large. Some modules allow the system administrator to request taking short-
cuts if these are known to be safe. It is then the system administrator's responsibility
to ensure the assumption is correct.
There are other modules where the implementation changed over time. If an implementation
used to sacrifice speed for memory consumption it might create problems if the preference
The /etc/default/nss file contains a number of variable assignments. Each variable con-
trols the behavior of one or more NSS modules. White spaces are ignored. Lines beginning
with '#' are treated as comments.
The variables currently recognized are:
NETID_AUTHORITATIVE = TRUE|FALSE
If set to TRUE, the NIS backend for the initgroups(3) function will accept the
information from the netid.byname NIS map as authoritative. This can speed up the
function significantly if the group.byname map is large. The content of the
netid.byname map is used as is. The system administrator has to make sure it is
SERVICES_AUTHORITATIVE = TRUE|FALSE
If set to TRUE, the NIS backend for the getservbyname(3) and getservbyname_r(3)
functions will assume that the services.byservicename NIS map exists and is author-
itative, particularly that it contains both keys with /proto and without /proto for
both primary service names and service aliases. The system administrator has to
make sure it is correctly generated.
SETENT_BATCH_READ = TRUE|FALSE
If set to TRUE, the NIS backend for the setpwent(3) and setgrent(3) functions will
read the entire database at once and then hand out the requests one by one from
memory with every corresponding getpwent(3) or getgrent(3) call respectively. Oth-
erwise each getpwent(3) or getgrent(3) call might result in a network communication
with the server to get the next entry.
The default configuration corresponds to the following configuration file:
This page is part of release 3.55 of the Linux man-pages project. A description of the
project, and information about reporting bugs, can be found at
Linux 2013-02-13 NSS(5)
All times are GMT -4. The time now is 01:33 AM.