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nss(5) File Formats 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 man-pages 6.9.1 2024-05-02 nss(5)
Pages that refer to this page: nsswitch.conf(5), systemd-resolved.service(8)
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HTML rendering created 2024-06-26 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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