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nsswitch.conf - configuration file for the name service switch

/etc/nsswitch.conf

The operating system uses a number of databases of information about hosts, ipnodes, users (passwd(4), shadow(4), and user_attr(4)), and groups. Data for these can come from a variety of sources: hostnames and host addresses, for example, can be found in /etc/hosts, NIS, NIS+, LDAP, DNS or Multicast DNS. Zero or more sources can be used for each database; the sources and their lookup order are specified in the /etc/nsswitch.conf file.

The following databases use the switch file:

Database	Used By
aliases	sendmail(1M)
auth_attr	getauthnam(3SECDB)
automount	automount(1M)
bootparams	rpc.bootparamd(1M)
ethers	ethers(3SOCKET)
group	getgrnam(3C)
hosts
gethostbyname(3NSL), getaddrinfo(3SOCKET). See Interaction with netconfig.
ipnodes	Same as hosts.
netgroup	innetgr(3C)
netmasks	ifconfig(1M)
networks	getnetbyname(3SOCKET)
passwd
getpwnam(3C), getspnam(3C), getauusernam(3BSM), getusernam(3SECDB)
printers
lp(1), lpstat(1), cancel(1), lpr(1B), lpq(1B), lprm(1B), in.lpd(1M), lpadmin(1M), lpget(1M), lpset(1M)
prof_attr	getprofnam(3SECDB), getexecprof(3SECDB)
project
getprojent(3PROJECT), getdefaultproj(3PROJECT), inproj(3PROJECT), newtask(1), setproject(3PROJECT)
protocols	getprotobyname(3SOCKET)
publickey	getpublickey(3NSL), secure_rpc(3NSL)
rpc	getrpcbyname(3NSL)
services	getservbyname(3SOCKET).
	See Interaction with netconfig.
user_attr	getuserattr(3SECDB)

The following sources can be used:

Source	Uses
files
/etc/hosts, /etc/passwd, /etc/inet/ipnodes, /etc/shadow, /etc/security/auth_attr, /etc/user_attr
nis	NIS(YP)
nisplus	NIS+
ldap	LDAP
ad	Active Directory
dns
Valid only for hosts and ipnodes. Uses the Internet Domain Name Service.
mdns
Valid only for hosts and ipnodes. Uses the Multicast Domain Name Service.
compat
Valid only for passwd and group. Implements + and -. See Interaction with +/- syntax.
user
Valid only for printers. Implements support for ${HOME}/.printers.

Note that /etc/inet/ipnodes is a symbolic link to /etc/hosts.

There is an entry in /etc/nsswitch.conf for each database. Typically these entries are simple, such as protocols: files or networks: files nisplus. However, when multiple sources are specified, it is sometimes necessary to define precisely the circumstances under which each source is tried. A source can return one of the following codes:

Status	Meaning
SUCCESS	Requested database entry was found.
UNAVAIL
Source is not configured on this system or internal failure.
NOTFOUND	Source responded "no such entry"
TRYAGAIN
Source is busy or not responding, might respond to retries.

For each status code, two actions are possible:

Action	Meaning
continue	Try the next source in the list.
return	Return now.

Additionally, for TRYAGAIN only, the following actions are possible:

Action	Meaning
forever	Retry the current source forever.
n
Retry the current source n more times, where n is an integer between 0 and MAX_INT (that is, 2.14 billion). After n retries has been exhausted, the TRYAGAIN action transitions to continue, until a future request receives a response, at which time TRYAGAIN=n is restored.

The complete syntax of an entry is:

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

For every status except TRYAGAIN, the action syntax is:

<action> ::= "return" | "continue"

For the TRYAGAIN status, the action syntax is:

<action> ::= "return" | "continue" | "forever" | <n>
<n> ::= 0...MAX_INT 

Each entry occupies a single line in the file. Lines that are blank, or that start with white space, are ignored. Everything on a line following a # character is also ignored; the # character can begin anywhere in a line, to be used to begin comments. The <database> and <source> names are case-sensitive, but <action> and <status> names are case-insensitive.

The library functions contain compiled-in default entries that are used if the appropriate entry in nsswitch.conf is absent or syntactically incorrect.

The default criteria for DNS and the NIS server in "DNS-forwarding mode" is [SUCCESS=return NOTFOUND=continue UNAVAIL=continue TRYAGAIN=3].

The default criteria for all other sources is [SUCCESS=return NOTFOUND=continue UNAVAIL=continue TRYAGAIN=forever].

The default, or explicitly specified, criteria are meaningless following the last source in an entry; and they are ignored, since the action is always to return to the caller irrespective of the status code the source returns.

In order to ensure that they all return consistent results, gethostbyname(3NSL), getaddrinfo(3SOCKET), getservbyname(3SOCKET), and netdir_getbyname(3NSL) functions are all implemented in terms of the same internal library function. This function obtains the system-wide source lookup policy for hosts, ipnodes, and services based on the inet family entries in netconfig(4) and uses the switch entries only if the netconfig entries have a - (hyphen) in the last column for nametoaddr libraries. See the Notes section in gethostbyname(3NSL) and getservbyname(3SOCKET) for details.

The NIS+ server can be run in YP-compatibility mode, where it handles NIS (YP) requests as well as NIS+ requests. In this case, the clients get much the same results (except for getspnam(3C)) from the nis source as from nisplus; however, nisplus is recommended instead of nis.

The NIS (YP) server can be run in DNS-forwarding mode, where it forwards lookup requests to DNS for host-names and -addresses that do not exist in its database. In this case, specifying nis as a source for hosts is sufficient to get DNS lookups; dns need not be specified explicitly as a source.

In SunOS 5.3 (Solaris 2.3) and compatible versions, the NIS+ server in NIS/YP-compatibility mode can also be run in DNS-forwarding mode (see rpc.nisd(1M)). Forwarding is effective only for requests originating from its YP clients; hosts policy on these clients should be configured appropriately.

When password aging is turned on, only a limited set of possible name services are permitted for the passwd: database in the /etc/nsswitch.conf file:

passwd:

passwd:

passwd:

passwd:

passwd:

passwd_compat:

passwd_compat:

You can add the ad keyword to any of the passwd configurations listed above. However, you cannot use the passwd command to change the password of an Active Directory (AD) user. If the ad keyword is found in the passwd entry during a password update operation, it is ignored. To update the password of an AD user, use the kpasswd(1) command.

Any other settings causes the passwd(1) command to fail when it attempts to change the password after expiration and prevents the user from logging in. These are the only permitted settings when password aging has been turned on. Otherwise, you can work around incorrect passwd: lines by using the -r repository argument to the passwd(1) command and using passwd -r repository to override the nsswitch.conf settings and specify in which name service you want to modify your password.

Releases prior to SunOS 5.0 did not have the name service switch but did allow the user some policy control. In /etc/passwd one could have entries of the form +user (include the specified user from NIS passwd.byname), -user (exclude the specified user) and + (include everything, except excluded users, from NIS passwd.byname). The desired behavior was often everything in the file followed by everything in NIS, expressed by a solitary + at the end of /etc/passwd. The switch provides an alternative for this case (passwd: files nis) that does not require + entries in /etc/passwd and /etc/shadow (the latter is a new addition to SunOS 5.0, see shadow(4)).

If this is not sufficient, the NIS/YP compatibility source provides full +/- semantics. It reads /etc/passwd for getpwnam(3C) functions and /etc/shadow for getspnam(3C) functions and, if it finds +/- entries, invokes an appropriate source. By default, the source is nis, but this can be overridden by specifying nisplus or ldap as the source for the pseudo-database passwd_compat.

Note that in compat mode, for every /etc/passwd entry, there must be a corresponding entry in the /etc/shadow file.

The NIS/YP compatibility source also provides full +/- semantics for group; the relevant pseudo-database is group_compat.

The compiled-in default entries for all databases use NIS (YP) as the enterprise level name service and are identical to those in the default configuration of this file:

passwd:

group:

hosts:

ipnodes:

networks:

protocols:

rpc:

ethers:

netmasks:

bootparams:

publickey:

netgroup:

automount:

aliases:

services:

printers:

auth_attr

prof_attr

project

Note that the files source for the ipnodes and hosts databases is identical, as /etc/inet/ipnodes is a symbolic link to /etc/hosts. Because other sources for the ipnodes and hosts databases are different, do not remove the ipnodes line from the /etc/nsswitch.conf file.

The policy nis [NOTFOUND=return] files implies: if nis is UNAVAIL, continue on to files, and if nis returns NOTFOUND, return to the caller. In other words, treat nis as the authoritative source of information and try files only if nis is down. This, and other policies listed in the default configuration above, are identical to the hard-wired policies in SunOS releases prior to 5.0.

If compatibility with the +/- syntax for passwd and group is required, simply modify the entries for passwd and group to:

passwd:

group:

If NIS+ is the enterprise level name service, the default configuration should be modified to use nisplus instead of nis for every database on client machines. The file /etc/nsswitch.nisplus contains a sample configuration that can be copied to /etc/nsswitch.conf to set this policy.

If LDAP is the enterprise level name service, the default configuration should be modified to use ldap instead of nis for every database on client machines. The file /etc/nsswitch.ldap contains a sample configuration that can be copied to /etc/nsswitch.conf to set this policy.

When using Active Directory, dns is required to perform hosts resolution.

If the use of +/- syntax is desired in conjunction with nisplus, use the following four entries:

passwd:

passwd_compat:

group:

group_compat:

In order to get information from the Internet Domain Name Service for hosts that are not listed in the enterprise level name service, NIS+ or LDAP, use the following configuration and set up the /etc/resolv.conf file (see resolv.conf(4) for more details):

hosts:

or

hosts:

Many of the databases have enumeration functions: passwd has getpwent(), hosts has gethostent(), and so on. These were reasonable when the only source was files but often make little sense for hierarchically structured sources that contain large numbers of entries, much less for multiple sources. The interfaces are still provided and the implementations strive to provide reasonable results, but the data returned can be incomplete (enumeration for hosts is simply not supported by the dns source), inconsistent (if multiple sources are used), formatted in an unexpected fashion (for a host with a canonical name and three aliases, the nisplus source returns four hostents, and they might not be consecutive), or very expensive (enumerating a passwd database of 5,000 users is probably a bad idea). Furthermore, multiple threads in the same process using the same reentrant enumeration function (getXXXent_r() are supported beginning with SunOS 5.3) share the same enumeration position; if they interleave calls, they enumerate disjoint subsets of the same database.

In general, the use of the enumeration functions is deprecated. In the case of passwd, shadow, and group, it might sometimes be appropriate to use fgetgrent(), fgetpwent(), and fgetspent() (see getgrnam(3C), getpwnam(3C), and getspnam(3C), respectively), which use only the files source.

A source named SSS is implemented by a shared object named nss_SSS.so.1 that resides in /usr/lib.

/etc/nsswitch.conf

/usr/lib/nss_compat.so.1

/usr/lib/nss_dns.so.1

/usr/lib/nss_files.so.1

/usr/lib/nss_mdns.so.1

/usr/lib/nss_nis.so.1

/usr/lib/nss_nisplus.so.1

/usr/lib/nss_ldap.so.1

/usr/lib/nss_ad.so.1

/usr/lib/nss_user.so.1

/etc/netconfig

/etc/nsswitch.files

/etc/nsswitch.nis

/etc/nsswitch.nisplus

/etc/nsswitch.ldap

/etc/nsswitch.ad

/etc/nsswitch.dns

kpasswd(1), ldap(1), newtask(1), NIS+(1), passwd(1), automount(1M), ifconfig(1M), mdnsd(1M), rpc.bootparamd(1M), rpc.nisd(1M), sendmail(1M), getauusernam(3BSM), getgrnam(3C), getnetgrent(3C), getpwnam(3C), getspnam(3C), gethostbyname(3NSL), getpublickey(3NSL), getrpcbyname(3NSL), netdir(3NSL), secure_rpc(3NSL), getprojent(3PROJECT), getdefaultproj(3PROJECT), inproj(3PROJECT), setproject(3PROJECT), getauthnam(3SECDB), getexecprof(3SECDB), getprofnam(3SECDB), getuserattr(3SECDB), getusernam(3SECDB), ethers(3SOCKET), getaddrinfo(3SOCKET), getnetbyname(3SOCKET), getprotobyname(3SOCKET), getservbyname(3SOCKET), auth_attr(4), hosts(4), netconfig(4), project(4), resolv.conf(4), user_attr(4), ypfiles(4), ad(5)

Within each process that uses nsswitch.conf, the entire file is read only once; if the file is later changed, the process continues using the old configuration.

The use of both nis and nisplus as sources for the same database is strongly discouraged since both the name services are expected to store similar information and the lookups on the database can yield different results depending on which name service is operational at the time of the request. The same applies for using ldap along with nis or nisplus.

Do not use the ldap and ad keywords together when the Solaris LDAP client uses schema mapping to talk to Active Directory.

Misspelled names of sources and databases are treated as legitimate names of (most likely nonexistent) sources and databases.

The following functions do not use the switch: fgetgrent(3C), fgetprojent(3PROJECT), fgetpwent(3C), fgetspent(3C), getpw(3C), putpwent(3C), shadow(4).