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NIS(7P)								       NIS(7P)

NAME    [Toc]    [Back]

     nis, yp, ypbind - Network Information Services Protocol (Client)

SYNOPSIS    [Toc]    [Back]


DESCRIPTION    [Toc]    [Back]

     The Network Information Services Protocol (NIS) is	a simple Sun RPC based
     protocol to fetch keyed data from a remote	host.  It is typically used to
     distribute	name service information in medium sized organizations.	 The
     data is maintained	on a single host (designated the NIS master), and is
     pushed occasionally to a list of slave servers.  Client systems
     dynamically locate	a server and request data given	a domain name, map
     name and key.  In Irix the	daemon nsd(1M) acts as both the	server and
     client side proxy for the protocol.  The server side is implemented in
     the nsd extension library nisserv(7P) while the client side and binding
     server are	implemented in the nsd extension library nis(7P).  This	manual
     page documents the	behavior of the	client side protocol library for the
     nsd daemon.  Applications which wish to make direct requests can still
     use the NIS API routines documented in ypclnt(3Y).

     The library /var/ns/lib/libns_nis.so is opened by the nsd(1M) daemon when
     nis is listed as the protocol for some map	in a nsswitch.conf file.  On
     first open	the library initialization procedure sets up a port to handle
     YPBIND RPC	requests, determines the domain	of the local system
     (domainname(1)), and attempts to locate the servers for the domain.

     The library contains code to fetch	data from a remote NIS server and
     present it	as lines from the configuration	file from which	it came.  The
     nsd daemon	then presents that data	in the filesystem mounted under	/ns.

     Extended attributes in the	nsswitch.conf file can be used to control the
     behavior of the NIS protocol.  Extended attributes	are simply lists of
     key/value pairs attached to each object in	the nsd	filesystem.  The
     attributes	supported in this library are:

	  This is the domainname given as a parameter to the remote name
	  server.  This	attribute is typically inherited from the daemon
	  depending on the nsswitch.conf file that is being read.  Given the
	  configuration	file /var/ns/domains/DOMAINNAME/nsswitch.conf the
	  attribute "domain" is	set to DOMAINNAME.  For	the default domain,
	  represented by the file /etc/nsswitch.conf, the domain attribute is
	  the same as the current system-wide domain as	set by the
	  domainname(1)	command.  Typically the	script /etc/init.d/network
	  sets it using	the value saved	in /var/yp/ypdomain on system startup.
	  A client system can be a member of multiple domains by including
	  multiple instances of	the nis	keyword	in the nsswitch.conf file
	       hosts: nis(domain=engr) nis(domain=corp)

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NIS(7P)								       NIS(7P)

	  The table attribute is typically inherited from the daemon based on
	  the line from	which this entry occurs	in the nsswitch.conf file.  In
	  the above example the	table attribute	would be set to	hosts.byname
	  or hosts.byaddr depending on the context of the request.  Because
	  the NIS protocol implementations historically	did not	contain	all
	  the tables that are considered standard in UNS this implementation
	  will fake the	tables:	services.byport, rpc.byname, and
	  group.bymember.  It will first try to	fetch data from	these tables,
	  and if returned the error YP_NOMAP it	will walk through the opposite
	  map looking for the specific key. The	attempted lookup of
	  services.byport, rpc.byname, and group.bymember can be skipped by
	  the no_pseudo_maps attribute.	 It will also swap services.byname
	  with services.byport since the NIS map which was called
	  services.byname in old implementation	was really indexed by

     key  The key attribute is set by the daemon on each request, and is
	  passed directly on to	the remote NIS server without change.

	  The nis_multicast attribute is an integer hop	count for the maximum
	  number of hops for multicast bind requests.  By default this is 32.
	  Setting the nis_multicast attribute to 0 will	result in no multicast
	  binding requests being sent.	This attribute must be set using the
	  -a command line option.

	  The nis_retries attribute is an integer counter which	controls how
	  many times a request is sent and how long the	request	waits for
	  binding to occur before returning an error.  The default is 5.

	  The nis_timeout attribute is an integer that determines the amount
	  of time that a nis request can take before rebinding.	  The default
	  is 1 second.	The total time that a nis request can take is
	  (nis_retries * nis_binding).

	  The nis_secure attribute is a	boolean	which specifies	that requests
	  for this map should originate	on a privileged	port, thus allowing
	  secure maps to be served (see	nisserv(7P)).

	  As with other	nsd methods, the query results are made	available
	  through the /ns filesystem and will by default be readable by
	  anyone.  Therefore, if the data in the served	map is sensitive (such
	  as for the shadow map), this attribute should	be combined with the
	  mode attribute in order to restrict the visibilty of the files in
	  the /ns filesystem.

									Page 2

NIS(7P)								       NIS(7P)

	  the nis_security attribute determines	if ypbind requests should be
	  honored.  This attribute should be set to one	of none, local,	or
	  any. This attribute must be set using	the -a command line option.

	  The nis_servers attribute is a space separated list of IP addresses,
	  or locally resolvable	host names for the systems which act as
	  servers for this domain.  If the nis_servers attribute is given then
	  the daemon will not send out a broadcast or multicast	request	for a
	  server, but will instead unicast binding requests to the listed
	  servers.  This may also be set by creating the file
	  /var/yp/binding/DOMAINNAME/ypservers for the domain you wish to
	  control.  This file is made up of a space separated list of
	  addresses, or	locally	resolvable names.  See ypservers(4) for	more
	  detailed information.

	  The null_extend_key attribute	specifies that the null	character
	  which	terminates the key is really part of the key.  Some
	  applications (such as	sendmail) have historically included the null
	  in the key so	this attribute provides	backward compatibility with
	  the old behavior.

	  The nis_enumerate_key	attribute is a boolean value that controls the
	  inclusion of keys in table enumeration data.	Specifying this
	  attribute is equivalent to the -k option to ypcat(1).	 If the
	  null_extend_key attribute is set, the	null in	the key	will be
	  excluded from	the enumeration	result.

	  The no_pseudo_maps attribute specifies that the initial lookup of
	  services.byport, rpc.byname, and group.bymember should be skipped
	  and that NSD should always attempt the workaround for	these
	  potentially non-existent maps.

	  The nis_maxfraglen attribute allows increasing the maximum record
	  fragment length the NIS client will allow on a reply from a TCP
	  based	request.  Currently the	only NIS procedure which uses TCP is
	  YPPROC_ALL. This procedure is	called when applications use the
	  getxxent() library calls.  A common and realtively obscure example
	  is when a user logs in, the getgrent function	is called to retrieve
	  the list of groups to	determine which	groups this user is a member
	  of.  If using	NIS to retrieve	the group list,	and the	NIS server is
	  sending very large fragments on the TCP stream, nsd's	NIS client
	  code,	as a security measure, will discard any	fragment which exceeds
	  it's maximum allowable fragment size.	The result in this instance
	  can be the user not seeing all the groups he/she belongs to via, for
	  example, the groups command.

									Page 3

NIS(7P)								       NIS(7P)

	  The vast majority of vendor's	NIS servers fragment the responses in
	  smaller sizes	typically no more than 8k per fragment.	However, there
	  is no	standard for how this must be done and some servers have been
	  known	to use much larger fragment sizes, and potentially, sending
	  the entire map in a single fragment. The nis_maxfraglen attribute
	  allows the flexibility of increasing (or decreasing) the default
	  limit	of 32k.

	  NOTE:	Should this attribute be used, some consideration should be
	  taken	in increasing this value. Theoretically	this fragment size can
	  be 2^31 as RPC uses the low order 31 bits of the fragment header to
	  specify the size. Increasing this limit too much can be detrimental
	  should the the YPPROC_ALL replies be spoofed with extremely large
	  fragment sizes.

ENABLING    [Toc]    [Back]

     The NIS functionality of nsd must be enabled via the chkconfig yp

NOTE    [Toc]    [Back]

     The daemon	nsd(1M)	uses this library to replace the ypbind	daemon from
     previous IRIX releases.  Similarly, nsd uses the nisserv(7P) library to
     replace the ypserv	daemon from previous releases.

FILES    [Toc]    [Back]


SEE ALSO    [Toc]    [Back]

     chkconfig(1M), nsd(1M), nsswitch.conf(4), nisserv(7P), ypservers(4)
     IRIX Admin: Networking and	Mail
     IRIX NIS Administration Guide

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