nsswitch.conf(4) nsswitch.conf(4)
NAME
nsswitch.conf - configuration file for the name service switch
SYNOPSIS
/etc/nsswitch.conf
The operating system uses a number of databases of information about hosts, ipnodes, users (passwd and shadow), 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, or DNS. Zero or
more sources may 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). See Interaction
with netconfig.
ipnodes getaddrinfo(3SOCKET)
netgroup innetgr(3C)
netmasks ifconfig(1M)
networks getnetbyname(3SOCKET)
passwd getpwnam(3C), getspnam(3C), getauuser-
nam(3BSM), getusernam(3SECDB)
printers lp(1), lpstat(1), cancel(1), lpr(1B),
lpq(1B), lprm(1B), in.lpd(1M), lpad-
min(1M), lpget(1M), lpset(1M)
prof_attr getprofnam(3SECDB), getexecprof(3SECDB)
project getprojent(3PROJECT), getdefault-
proj(3PROJECT), inproj(3PROJECT), new-
task(1), setproject(3PROJECT)
protocols getprotobyname(3SOCKET)
publickey getpublickey(3NSL), secure_rpc(3NSL)
rpc getrpcbyname(3NSL)
services getservbyname(3SOCKET).
See Interaction with netconfig.
The following sources may be used:
Source Uses
files /etc/hosts, /etc/passwd,
/etc/inet/ipnodes, /etc/shadow
nis NIS(YP)
nisplus NIS+
ldap LDAP
dns Valid only for hosts and ipnodes.
Uses the Internet Domain Name
Service.
compat Valid only for passwd and group.
Implements "+" and "-". See
Interaction with +/- syntax.
user Valid only for printers. Imple-
ments support for ${HOME}/.print-
ers.
There is an entry in /etc/nsswitch.conf for each database. Typically these entries will be 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 will be 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 TRYA-
GAIN=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 fol-
lowing 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 syntacti-
cally 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.
Interaction with netconfig
In order to ensure that they all return consistent results, gethostbyname(3NSL), getaddrinfo(3SOCKET), getservbyname(3SOCKET), and net-
dir_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 "-" in the last column for nametoaddr libraries. See the section in gethostbyname(3NSL) and getservby-
name(3SOCKET) for details.
YP-compatibility Mode
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".
Interaction with server in DNS-forwarding Mode
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.
Interaction with Password Aging
When password aging is turned on, only a limited set of possible name services are permitted for the passwd: database in the /etc/nss-
witch.conf file:
passwd: files
passwd: files nis
passwd: files nisplus
passwd: files ldap
passwd: compat
passwd_compat: nisplus
passwd_compat: ldap
Any other settings will cause the passwd(1) command to fail when it attempts to change the password after expiration and will prevent the
user from logging in. These are the only permitted settings when password aging has been turned on. Otherwise, you can work around incor-
rect passwd: lines by using the -r repository argument to the passwd(1) command and using passwd -r repository to override the nss-
witch.conf settings and specify in which name service you want to modify your password.
Interaction with +/- syntax
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 every-
thing, 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 may 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.
Useful Configurations
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: files nis
group: files nis
hosts: nis [NOTFOUND=return] files
ipnodes: nis [NOTFOUND=return] files
networks: nis [NOTFOUND=return] files
protocols: nis [NOTFOUND=return] files
rpc: nis [NOTFOUND=return] files
ethers: nis [NOTFOUND=return] files
netmasks: nis [NOTFOUND=return] files
bootparams: nis [NOTFOUND=return] files
publickey: nis [NOTFOUND=return] files
netgroup: nis
automount: files nis
aliases: files nis
services: files nis
printers: user files nis nisplus
auth_attr files nis
prof_attr files nis
project files nis
The policy "nis [NOTFOUND=return] files" implies "if nis is UNAVAIL, continue on to files, and if nis returns NOTFOUND, return to the call-
er; 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: compat
group: compat
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.
If the use of +/- syntax is desired in conjunction with nisplus, use the following four entries:
passwd: compat
passwd_compat: nisplus OR ldap
group: compat
group_compat: nisplus OR ldap
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: nisplus dns [NOTFOUND=return] files
or
hosts: ldap dns [NOTFOUND=return] files
Enumeration - getXXXent()
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
may 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 will return four hostents, and they may
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 will 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 may 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 Configuration file.
/usr/lib/nss_compat.so.1 Implements "compat" source.
/usr/lib/nss_dns.so.1 Implements "dns" source.
/usr/lib/nss_files.so.1 Implements "files" source.
/usr/lib/nss_nis.so.1 Implements "nis" source.
/usr/lib/nss_nisplus.so.1 Implements "nisplus" source.
/usr/lib/nss_ldap.so.1 Implements "ldap" source.
/usr/lib/nss_user.so.1 Implements "user" source.
/etc/netconfig Configuration file for netdir(3NSL) functions that redirects hosts/devices policy to the switch.
/etc/nsswitch.files Sample configuration file that uses "files" only.
/etc/nsswitch.nis Sample configuration file that uses "files" and "nis".
/etc/nsswitch.nisplus Sample configuration file that uses "files" and "nisplus".
/etc/nsswitch.ldap Sample configuration file that uses "files" and "ldap".
/etc/nsswitch.dns Sample configuration file that uses "files" and "dns" (but only for hosts:).
ldap(1), newtask(1), nis+(1), passwd(1), automount(1M), ifconfig(1M), rpc.bootparamd(1M), rpc.nisd(1M), sendmail(1M), getauuser-
nam(3BSM)getgrnam(3C), getnetgrent(3C), getpwnam(3C), getspnam(3C), gethostbyname(3NSL), getpublickey(3NSL), getrpcbyname(3NSL), net-
dir(3NSL), secure_rpc(3NSL), getprojent(3PROJECT), getdefaultproj(3PROJECT), inproj(3PROJECT), setproject(3PROJECT), getauthnam(3SECDB),
getexecprof(3SECDB), getprofnam(3SECDB), getusernam(3SECDB), ethers(3SOCKET), getaddrinfo(3SOCKET), getnetbyname(3SOCKET), getprotoby-
name(3SOCKET), getservbyname(3SOCKET), netconfig(4), project(4), resolv.conf(4), ypfiles(4)
Within each process that uses nsswitch.conf, the entire file is read only once; if the file is later changed, the process will continue
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 may 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.
Misspelled names of sources and databases will be 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).
25 May 2005 nsswitch.conf(4)