NSSWITCH.CONF (5) | | Unix Manual Pages

NSSWITCH.CONF (5) | | Unix Manual Pages | :man▋

NAME

nsswitch.conf - name-service switch configuration file

Description
Sources
Databases
Status codes
Actions
Format of file
Compat mode: +/- syntax
Notes
Default source lists
Files
Examples
Notes
See Also
History
Authors

DESCRIPTION

The nsswitch.conf file specifies how the nsdispatch(3) (name-service switch dispatcher) routines in the C library should operate.

The configuration file controls how a process looks up various databases containing information regarding hosts, users (passwords), groups, etc. Each database comes from a source (such as local files, DNS, and NIS), and the order to look up the sources is specified in nsswitch.conf.

Each entry in nsswitch.conf consists of a database name, and a space separated list of sources. Each source can have an optional trailing criterion that determines whether the next listed source is used, or the search terminates at the current source. Each criterion consists of one or more status codes, and actions to take if that status code occurs.

Sources

The following sources are implemented:

Source
	Description
files	Local files, such as `/etc/hosts`, and `/etc/passwd`.
dns	Internet Domain Name System. "hosts" and 'networks' use IN class entries, all other databases use HS class (Hesiod) entries.
nis	NIS (formerly YP)
compat
	support '+/-' in the "passwd" and "group" databases. If this is present, it must be the only source for that entry.

Databases

The following databases are used by the following C library functions:

Database
	"Used by"
group	getgrent(3)
hosts	gethostbyname(3)
networks
	getnetbyname(3)
passwd	getpwent(3)
shells	getusershell(3)

Status codes

The following status codes are available:

Status	Description
success	The requested entry was found.
notfound
	The entry is not present at this source.
tryagain
	The source is busy, and may respond to retries.
unavail	The source is not responding, or entry is corrupt.

Actions

For each of the status codes, one of two actions is possible:

Action	Description
continue
	Try the next source
return	Return with the current result

Format of file

A BNF description of the syntax of nsswitch.conf is:

<entry>	::= <database> ":" [<source> [<criteria>]]*
<criteria>	::= "[" <criterion>+ "]"
<criterion>
	::= <status> "=" <action>
<status>	::= "success" \| "notfound" \| "unavail" \| "tryagain"
<action>	::= "return" \| "continue"

Each entry starts on a new line in the file. A '#' delimits a comment to end of line. Blank lines are ignored. A '\' at the end of a line escapes the newline, and causes the next line to be a continuation of the current line. All entries are case-insensitive.

The default criteria is to return on "success", and continue on anything else (i.e, "[success=return notfound=continue unavail=continue tryagain=continue]").