YPSERV(8) Maintenance Procedures YPSERV(8)


ypserv, ypxfrd - NIS server and binder processes


/usr/lib/netsvc/yp/ypserv [-dv] [-i | -I] [-r | -R]



The Network Information Service (NIS) provides a simple network lookup
service consisting of databases and processes. The databases are ndbm
files in a directory tree rooted at /var/yp. See ndbm(3C). These files
are described in ypfiles(5). The processes are /usr/lib/netsvc/yp/ypserv,
the NIS database lookup server, and /usr/lib/netsvc/yp/ypbind, the NIS
binder. The programmatic interface to the NIS service is described in
ypclnt(3NSL). Administrative tools are described in yppoll(8),
yppush(8), ypset(8), ypxfr(8), and ypwhich(1). Tools to see the contents
of NIS maps are described in ypcat(1), and ypmatch(1). Database
generation and maintenance tools are described in ypinit(8), ypmake(8),
and makedbm(8).

The ypserv utility is a daemon process typically activated at system
startup from svc:/network/nis/server:default. Alternatively, you can, as
the root user, start NIS services using ypstart(8) from the command-line.
ypserv runs only on NIS server machines with a complete NIS database. You
can halt all NIS services using the ypstop(8) command.

The ypxfrd utility transfers entire NIS maps in an efficient manner. For
systems that use this daemon, map transfers are 10 to 100 times faster,
depending on the map. To use this daemon, be sure ypxfrd is running on
the master server. See /usr/lib/netsvc/yp/ypstart. ypxfr attempts to use
ypxfrd first. If that fails, it prints a warning, then uses the older
transfer method.

The ypserv daemon's primary function is to look up information in its
local database of NIS maps.

The operations performed by ypserv are defined for the implementor by the
YP Protocol Specification, and for the programmer by the header file

Communication to and from ypserv is by means of RPC calls. Lookup
functions are described in ypclnt(3NSL), and are supplied as C-callable
functions in the libnsl(3LIB) library. There are four lookup functions,
all of which are performed on a specified map within some NIS domain:
yp_match(3NSL), yp_first(3NSL), yp_next(3NSL), and yp_all(3NSL). The
yp_match operation takes a key, and returns the associated value. The
yp_first operation returns the first key-value pair from the map, and
yp_next can be used to enumerate the remainder. yp_all ships the entire
map to the requester as the response to a single RPC request.

A number of special keys in the DBM files can alter the way in which
ypserv operates. The keys of interest are:

The presence of this key causes ypserv to forward to
a DNS server host lookups that cannot be satisfied
by the DBM files.

This key causes ypserv to answer only questions
coming from clients on reserved ports.

This is a special key in the form, YP_MULTI_hostname
addr1,...,addrN. A client looking for hostname
receives the closest address.

Two other functions supply information about the map, rather than map
entries: yp_order(3NSL), and yp_master(3NSL). In fact, both order number
and master name exist in the map as key-value pairs, but the server will
not return either through the normal lookup functions. If you examine the
map with makedbm(8), however, they are visible. Other functions are used
within the NIS service subsystem itself, and are not of general interest
to NIS clients. These functions include do_you_serve_this_domain?,
transfer_map, and reinitialize_internal_state.

On start up, ypserv checks for the existence of the NIS to LDAP (N2L)
configuration file /var/yp/NISLDAPmapping. If it is present then a master
server starts in N2L mode. If the file is not present it starts in
"traditional" (non N2L) mode. Slave servers always start in traditional

In N2L mode, a new set of map files, with an LDAP_ prefix, are generated,
based on the contents of the LDAP DIT. The old map files, NIS source
files and ypmake(8) are not used.

It is possible that ypmake(8) can be accidentally run in N2L mode. If the
occurs, the old style map files are overwritten. That the map files are
overwritten is harmless. However, any resulting yppush(8) operation will
push information based on the DIT rather than the source files. The user
may not expect information based on the DIT. ypserv keeps track of the
last modification date of the old style map files. If the map files have
been updated, a warning is logged that suggests that the user call yppush
directly instead of ypmake.

If a server attempts to run in N2L mode and a LDAP server cannot be
contacted, it behaves as follows:

1. When ypserv is started, a warning will be logged.

2. When a NIS read access is made and the TTL entry has expired,
a warning is logged.Information that is returned from the
cache has not been updated.

3. When a NIS write access is made, a warning is logged. The
cache will not be updated, and a NIS failure will be returned.

If ypxfrd is running in N2L mode and is asked to transfer a map, ypxfrd
first checks whether the map is out of date. If the map is out of date,
ypxfrd initiates an update from the DIT. ypxfrd cannot wait for the
update to complete. If ypxfrd waited, the client end ypxfr operation
could time out. To prevent ypxfrd from timing out, the existing map is
transferred from the cache. The most up to date map will be transferred
on subsequent ypxfrd operations.


The NIS service should go to the DNS for more host information.
This requires the existence of a correct /etc/resolv.conf file
pointing to a DNS server. This option turns on DNS forwarding
regardless of whether or not the YP_INTERDOMAIN flag is set in the
hosts maps. See makedbm(8). In the absence of an /etc/resolv.conf
file, ypserv complains, but ignores the -d option.

If in N2L mode, initialize the NIS related parts of the DIT based
on the current, non LDAP_ prefixed, map files. The LDAP_ prefixed
maps are not created or updated. If you require that LDAP_
prefixed maps be updated or created, then use the -ir option.

The -i option does not attempt to create any NIS domain or
container objects. If any NIS domain or container objects have not
already been created, then errors will occur, as entries are
written to nonexistent containers.

Identical to -i, except that any missing domain and container
objects are created.

If in N2L mode, then refresh the LDAP_ prefixed map files based on
the contents of the DIT.

If both -i and -r are specified in N2L mode, then the DIT will
first be initialized from the current non LDAP_ prefixed map
files. A new set of LDAP_ prefixed maps will then be generated
from the contents of the DIT. A new set of LDAP_ prefixed maps is
required when moving from traditional NIS to N2L mode NIS.

Identical to -ir, except that any missing domain and container
objects are created.

Operate in the verbose mode, printing diagnostic messages to

When run with the -i, -r, -I, -ir or -Ir options, the ypserv command runs
in the foreground and exits once map initialization has been completed.
Once the ypserv command exits, the user knows the maps are ready and can
restart ypserv and the other yp daemons by running ypstart(8).

If there is a requirement to initialize the DIT from the NIS source
files, which may have been modified since the maps were last remade, run
ypmake before running ypserv -i or ypserv -ir. ypmake regenerated old
style NIS maps. Then ypserv -ir dumps them into the DIT. When the -ir
option is used, the LDAP_ prefixe maps are also generated or updated.
Since these maps will be more recent than the old style maps, ypmake will
not be reported as erroneous when it is run.



Defines the hosts and networks that are granted access to information
in the served domain. It is read at startup time by both ypserv and


If the /var/yp/ypserv.log file exists when ypserv starts up, log
information is written to it when error conditions arise.


Lists the NIS server hosts that ypbind can bind to.


svcs(1), ypcat(1), ypmatch(1), ypwhich(1), ndbm(3C), libnsl(3LIB),
ypclnt(3NSL), NISLDAPmapping(5), securenets(5), ypfiles(5), ypserv(5),
attributes(7), smf(7), domainname(8), makedbm(8), svcadm(8), ypbind(8),
ypinit(8), ypmake(8), yppoll(8), yppush(8), ypset(8), ypstart(8),
ypstop(8), ypxfr(8)


ypserv supports multiple domains. The ypserv process determines the
domains it serves by looking for directories of the same name in the
directory /var/yp. It replies to all broadcasts requesting yp service for
that domain.

The Network Information Service (NIS) was formerly known as Sun Yellow
Pages (YP). The functionality of the two remains the same; only the name
has changed. The name Yellow Pages is a registered trademark in the
United Kingdom of British Telecommunications PLC, and must not be used
without permission.

NIS uses ndbm() files to store maps. Therefore, it is subject to the 1024
byte limitations described in the USAGE and NOTES sections of the
ndbm(3C) man page.

The NIS server service is managed by the service management facility,
smf(7), under the service identifier:


Administrative actions on this service, such as enabling, disabling, or
requesting restart, can be performed using svcadm(8). The service's
status can be queried using the svcs(1) command.

December 15, 2004 YPSERV(8)