Section: Linux Programmer's Manual (5)
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:
The default configuration corresponds to the following configuration file:
NETID_AUTHORITATIVE=FALSE SERVICES_AUTHORITATIVE=FALSE SETENT_BATCH_READ=FALSE
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