---
name: "nsswitch.conf"
section: "5"
platform: "freebsd"
package: "base"
version: "16.0-CURRENT-20261027-61c70dc16a79"
release: "FreeBSD 16.0-CURRENT (2026-10-27)"
platforms: ["linux", "freebsd"]
url: "https://new.carta.tech/nsswitch.conf"
---

# nsswitch.conf(5)

name-service switch configuration file

## NAME

**nsswitch.conf** – name-service switch configuration file

## DESCRIPTION

The **nsswitch.conf** file specifies how the [nsdispatch(3)](/nsdispatch/3.md) (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, NIS , and cache), 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 as part of the base system:

- **Source**

  **Description**

- files

  Local files, such as */etc/hosts*, and */etc/passwd*.

- db

  Local database.

- 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.

- cache

  makes use of the [nscd(8)](/nscd/8.md) daemon.

Additional sources might be provided by third party software.

### Databases

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

- **Database**

  **Used by**

- group

  [getgrent(3)](/getgrent/3.md), [getgrent\_r(3)](/getgrent_r/3.md), [getgrgid\_r(3)](/getgrgid_r/3.md), [getgrnam\_r(3)](/getgrnam_r/3.md), [setgrent(3)](/setgrent/3.md), [endgrent(3)](/endgrent/3.md)

- hosts

  [getaddrinfo(3)](/getaddrinfo/3.md), [gethostbyaddr(3)](/gethostbyaddr/3.md), [gethostbyaddr\_r(3)](/gethostbyaddr_r/3.md), [gethostbyname(3)](/gethostbyname/3.md), [gethostbyname2(3)](/gethostbyname2/3.md), [gethostbyname\_r(3)](/gethostbyname_r/3.md), [getipnodebyaddr(3)](/getipnodebyaddr/3.md), [getipnodebyname(3)](/getipnodebyname/3.md)

- networks

  [getnetbyaddr(3)](/getnetbyaddr/3.md), [getnetbyaddr\_r(3)](/getnetbyaddr_r/3.md), [getnetbyname(3)](/getnetbyname/3.md), [getnetbyname\_r(3)](/getnetbyname_r/3.md)

- passwd

  [getpwent(3)](/getpwent/3.md), [getpwent\_r(3)](/getpwent_r/3.md), [getpwnam\_r(3)](/getpwnam_r/3.md), [getpwuid\_r(3)](/getpwuid_r/3.md), [setpwent(3)](/setpwent/3.md), [endpwent(3)](/endpwent/3.md)

- shells

  [getusershell(3)](/getusershell/3.md)

- services

  [getservent(3)](/getservent/3.md)

- rpc

  [getrpcbyname(3)](/getrpcbyname/3.md), [getrpcbynumber(3)](/getrpcbynumber/3.md), [getrpcent(3)](/getrpcent/3.md)

- proto

  [getprotobyname(3)](/getprotobyname/3.md), [getprotobynumber(3)](/getprotobynumber/3.md), [getprotoent(3)](/getprotoent/3.md)

- netgroup

  [getnetgrent(3)](/getnetgrent/3.md), [getnetgrent\_r(3)](/getnetgrent_r/3.md), [setnetgrent(3)](/setnetgrent/3.md), [endnetgrent(3)](/endnetgrent/3.md), [innetgr(3)](/innetgr/3.md)

### 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, \[success=return notfound=continue unavail=continue tryagain=continue\]).

### Cache

You can enable caching for the particular database by specifying “cache” in the **nsswitch.conf** file. It should come after “files”, but before remote sources like “nis”. You should also enable caching for this database in [nscd.conf(5)](/nscd.conf/5.md). If for a particular query “cache” source returns success, then no further sources are queried. On the other hand, if there are no previously cached data, the query result will be placed into the cache right after all other sources are processed. Note that “cache” requires the [nscd(8)](/nscd/8.md) daemon to be running.

### Compat mode: +/- syntax

In historical multi-source implementations, the ‘+’ and ‘-’ characters are used to specify the importing of user password and group information from NIS . Although **nsswitch.conf** provides alternative methods of accessing distributed sources such as NIS , specifying a sole source of “compat” will provide the historical behaviour.

An alternative source for the information accessed via ‘+/-’ can be used by specifying “passwd\_compat: source”. “source” in this case can be ‘dns’, ‘nis’, or any other source except for ‘files’ and ‘compat’.

### Notes

Historically, many of the databases had enumeration functions, often of the form **getXXXent**(). These made sense when the databases were in local files, but do not make sense or have lesser relevance when there are possibly multiple sources, each of an unknown size. The interfaces are still provided for compatibility, but the source may not be able to provide complete entries, or duplicate entries may be retrieved if multiple sources that contain similar information are specified.

To ensure compatibility with previous and current implementations, the “compat” source must appear alone for a given database.

### Default source lists

If, for any reason, **nsswitch.conf** does not exist, or it has missing or corrupt entries, [nsdispatch(3)](/nsdispatch/3.md) will default to an entry of “files” for the requested database. Exceptions are:

- **Database**

  **Default source list**

- group

  compat

- group\_compat

  nis

- hosts

  files dns

- passwd

  compat

- passwd\_compat

  nis

- services

  compat

- services\_compat

  nis

## FILES

- */etc/nsswitch.conf*

  The file **nsswitch.conf** resides in */etc*.

## EXAMPLES

To lookup hosts in */etc/hosts* , then in cache, and then from the DNS, and lookup user information from NIS then files, use:

- hosts:

  files cache dns

- passwd:

  nis \[notfound=return\] files

- group:

  nis \[notfound=return\] files

The criteria “\[notfound=return\]” sets a policy of "if the user is notfound in nis, do not try files." This treats nis as the authoritative source of information, except when the server is down.

## NOTES

The **nsswitch.conf** file is parsed by each program only once. Subsequent changes will not be applied until the program is restarted.

If system got compiled with *WITHOUT\_NIS* you have to remove ‘nis’ entries.

FreeBSD's Standard C Library (libc, -lc) provides stubs for compatibility with NSS modules written for the GNU C Library **nsswitch** interface. However, these stubs only support the use of the “passwd” and “group” databases.

## SEE ALSO

[nsdispatch(3)](/nsdispatch/3.md), [nscd.conf(5)](/nscd.conf/5.md), [resolv.conf(5)](/resolv.conf/5.md), [nscd(8)](/nscd/8.md), [ypbind(8)](/ypbind/8.md)

## HISTORY

The **nsswitch.conf** file format first appeared in FreeBSD 5.0. It was imported from the NetBSD Project, where it appeared first in NetBSD 1.4.

## AUTHORS

Luke Mewburn ⟨*lukem@netbsd.org*⟩ wrote this freely distributable name-service switch implementation, using ideas from the ULTRIX svc.conf(5) and Solaris nsswitch.conf(4) manual pages.