illumos: manual page: nsswitch.conf.5

NSSWITCH.CONF(5) File Formats and Configurations NSSWITCH.CONF(5)

NAME

nsswitch.conf - configuration file for the name service switch

SYNOPSIS

/etc/nsswitch.conf

DESCRIPTION

The operating system uses a number of databases of information about
hosts, ipnodes, users (passwd(5), shadow(5), and user_attr(5)), 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, 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(8)
auth_attr getauthnam(3SECDB)
automount automount(8)
bootparams rpc.bootparamd(8)
ethers ethers(3SOCKET)
group getgrnam(3C)
hosts gethostbyname(3NSL),
getaddrinfo(3SOCKET). See
Interaction with netconfig.
ipnodes Same as hosts.
netgroup innetgr(3C)
netmasks ifconfig(8)
networks getnetbyname(3SOCKET)
passwd getpwnam(3C), getspnam(3C),
getusernam(3SECDB)
printers lp(1), lpstat(1), cancel(1),
lpr(1B), lpq(1B), lprm(1B),
in.lpd(8), lpadmin(8),
lpget(8), lpset(8)
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)
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. 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.

Interaction with netconfig

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(5) 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.

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.

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/nsswitch.conf
file:

passwd:
files

passwd:
files nis

passwd:
files ldap

passwd:
compat

passwd_compat:
ldap

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.

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 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(5)).

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 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

auth_attr
files nis

prof_attr
files nis

project
files nis

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:
compat

group:
compat

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 LDAP, use the
following four entries:

passwd:
compat

passwd_compat:
ldap

group:
compat

group_compat:
ldap

In order to get information from the Internet Domain Name Service for
hosts that are not listed in the enterprise level name service, such as
LDAP, use the following configuration and set up the /etc/resolv.conf
file (see resolv.conf(5) for more details):

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 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, 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.

FILES

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_mdns.so.1
Implements mdns source.

/usr/lib/nss_nis.so.1
Implements nis source.

/usr/lib/nss_ldap.so.1
Implements ldap source.

/usr/lib/nss_ad.so.1
Implements ad 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.ldap
Sample configuration file that uses files
and ldap.

/etc/nsswitch.ad
Sample configuration file that uses files
and ad.

/etc/nsswitch.dns
Sample configuration file that uses files,
dns and mdns (dns and mdns only for hosts).

NOTES

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.

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(5).

March 6, 2017 NSSWITCH.CONF(5)