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
naturally 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
shortcuts 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 is switched.
The /etc/default/nss file contains a number of variable assignments.
Each variable controls 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 correctly generated.
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 authoritative,
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. Otherwise, each getpwent(3) or getgrent(3) call
might result in a network communication with the server to get
the next entry.
/etc/default/nss
The default configuration corresponds to the following configuration
file:
NETID_AUTHORITATIVE=FALSE
SERVICES_AUTHORITATIVE=FALSE
SETENT_BATCH_READ=FALSE
nsswitch.conf
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Linux 2013-02-13 NSS(5)
Pages that refer to this page: nsswitch.conf(5), systemd-resolved.service(8)