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ypserv(8)							     ypserv(8)

NAME
       ypserv,	ypbind	-  Network Information Service (NIS) server and binder
       processes

SYNOPSIS
       /usr/sbin/ypserv [-a method]

       /usr/sbin/ypbind	  [-s	 -S	domainname,servername1,servername2...]
       [-ypset	| -ypsetme]

OPTIONS
       Specifies  the  database	 routines used to store NIS maps.  The choices
       are: btree -- Recommended when  creating	 and  maintaining  very	 large
       maps.   dbm/ndbm	 --  For  backward compatibility. This is the default.
       hash -- A potentially quicker method for managing small	maps.	Allows
       the  ypbind  process to run in a secure mode.  This requires the server
       to use a secure port.  Allows the system administrator to  lock	ypbind
       to  a  particular domain and set of servers.  Up to four servers can be
       specified     as	    follows:	 /usr/sbin/ypbind      -S      domain‐
       name,server1,server2,server3,server4

	      Note  that  there	 cannot be any spaces around the commas in the
	      command line. The -S option ensures that this system only	 binds
	      to the specified domain and to one of the specified servers. The
	      servers used with the -S option must have entries in  the	 local
	      /etc/hosts  file.	  ypbind  accepts  all	ypset requests, unless
	      restricted by the -S option.  ypbind accepts  only  local	 ypset
	      requests.

					    Note

	      If  neither  -ypset  nor -ypsetme are specified, ypbind does not
	      accept ypset requests to bind to a particular server.

DESCRIPTION
       The Network Information	Service	 (NIS)	provides  a  distributed  data
       lookup  service	for  sharing data among networked systems. NIS data is
       stored in database files called maps. The  databases  consist  of  dbm,
       btree,  or  hash files stored in the /var/yp/src directory. These files
       are described in ypfiles(4).

       The NIS daemons are /usr/sbin/ypserv, the NIS database  lookup  server,
       and  /usr/sbin/ypbind, the NIS binder. The software interface to NIS is
       described  in  ypclnt(3).  Administrative  tools	  are	described   in
       yppush(8),  ypxfr(8),  yppoll(8), and ypwhich(1). Tools to see the con‐
       tents of NIS maps are described in ypcat(1), and	 ypmatch(1).  Database
       generation  and	maintenance  tools  are	 described  in	ypmake(8), and
       makedbm(8).

       Both the ypserv and ypbind daemons are activated at system startup time
       by  /sbin/init.d/nis.   The  ypserv  daemon  runs only on an NIS server
       machine with a complete NIS database. The ypbind	 daemon	 runs  on  all
       machines using NIS, both NIS servers and clients.

       The [-a method] option to ypserv tells ypserv which format the maps are
       stored in; either btree, dbm, or hash.

   ypserv Daemon
       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 programmer in the <rpcsvc/yp_prot.h> header file.

       Communication with ypserv is by means of RPC calls.   Lookup  functions
       are described in ypclnt(3), and are supplied as C-callable functions in
       /libc.

       There are four lookup functions, all of which are performed on a speci‐
       fied map within an NIS domain: Match, Get_first, Get_next, and Get_all.
       The Match operation takes a key, and returns the associated value.  The
       Get_first  operation returns the first key-value pair from the map, and
       the Get_next operation  returns	the  remaining	key-value  pairs.  The
       Get_all operation ships the entire map to the requester.

       Two  other  functions supply information about the map, rather than the
       map entries: Get_order_number and Get_master_name. Both the order  num‐
       ber  and	 the  master name exist in the map as key-value pairs, but the
       server will not return either through the usual lookup  functions.   If
       the map is examined with makedbm(8), however, they are visible.

       Other  functions	 are used within the NIS subsystem itself, and are not
       of   general   interest	 to   NIS   clients.	They	include	   the
       Do_you_serve_this_domain?,   the	  Transfer_map,	  and  the  Reinitial‐
       ize_internal_state functions.

   securenets File
       The /etc/yp/securenets file contains a list of subnets that are consid‐
       ered  trusted  and that are allowed to access NIS data using the ypserv
       and ypxfrd daemons. It is a user-created file that resides  on  an  NIS
       master server and any slave servers.

       If  the	/etc/yp/securenets file does not exist, or exists but contains
       no subnets, all IP addresses  are  accepted.  However,  anyone  on  the
       Internet	 that  knows  the  NIS	server address and the domain name can
       obtain  NIS  served  data,  including  the  passwd  file.   Using   the
       securenets file is a recommended method of security.

       If  you	want  an  NIS  slave  server, use a /etc/yp/securenets file to
       restrict IP addresses to	 which	it  serves.   The  slave  server's  IP
       address	 must  be  in  the  authorization  range  of  entries  in  the
       /etc/yp/securenets file on the NIS master server.

       Each entry in the /etc/yp/securenets file contains an  IP  subnet  mask
       and  a corresponding subnet IP address separated by at least one space.
       Lines that do not begin with a digit are considered comments.  The file
       has the following format:

       subnet_mask     subnet_ip_address

       In  the	following  securenets  file example, the first two lines allow
       only  those  IP	addresses  that	 are  within  the  subnet  128.30  and
       128.211.10  range  to  access the NIS files.  The third line authorizes
       the one host at address 128.211.5.6.

       255.255.0.0   128.30.0.0	 255.255.255.0	128.211.10.0   255.255.255.255
       128.211.5.6

   ypbind Daemon
       The  ypbind  daemon's  function is to remember information that enables
       client processes on a single node to communicate with a ypserv process.
       The  ypbind function must run on every machine that has NIS client ser‐
       vice requirements.  The ypbind function	must  be  started  through  an
       entry in the /sbin/init.d/nis file.

       The  information	 ypbind remembers is called a binding, the association
       of a domain name with the internet address of the NIS server,  and  the
       port  on that host at which the ypserv process is listening for service
       requests.  The process of binding is driven by client requests.	 As  a
       request	for  an unbound domain comes in, the ypbind process broadcasts
       on the net trying to find a ypserv process that serves maps within that
       domain.	 Since	the binding is established by broadcasting, there must
       be at least one ypserv process on every net.  Once a domain is bound by
       a particular ypbind, that same binding is given to every client process
       on the node. The ypbind process on the local node or a remote node  may
       be  queried  for	 the  binding  of  a  particular  domain  by using the
       ypwhich(1) command.

       Bindings are verified before they are given out to  a  client  process.
       If  ypbind  is unable to speak to the ypserv process it is bound to, it
       marks the domain as unbound, tells the client process that  the	domain
       is unbound, and tries to bind the domain once again.  Requests received
       for an unbound domain will fail immediately. In general, a bound domain
       is marked as unbound when the node running ypserv crashes or gets over‐
       loaded.	When the node gets overloaded, ypbind will try to bind to  any
       NIS server (typically one that is less-heavily loaded) available on the
       net.

       The ypbind process also accepts requests to set its binding for a  par‐
       ticular	domain.	 The request is usually generated by the NIS subsystem
       itself.

RESTRICTIONS
       You must use the same database format for each  map  in	a  domain.  In
       addition, a server serving multiple NIS domains must use the same data‐
       base format for all domains.

       Although a Tru64 UNIX NIS server that takes advantage  of  btree	 files
       will be able to store very large maps, NIS slave servers that lack this
       feature might have a much smaller limit on the number  of  map  entries
       they  can handle.  It may not be possible to distribute very large maps
       from a Tru64 UNIX NIS master server to a slave server that  lacks  sup‐
       port  for  very	large  maps.   NIS  clients  are not affected by these
       enhancements.

EXAMPLES
       The following is an example of the ypserv command used with  the	 btree
       format database routine to store NIS maps.  ypserv -a b

FILES
       If  this	 file exists when ypserv starts up, log information is written
       to ypserv.log when error conditions occur.  User-created	 file  on  the
       NIS  server that contains a list of trusted subnets that are allowed to
       access NIS data using the ypserv and ypxfrd daemons.

SEE ALSO
       Commands: ypcat(1),  ypmatch(1),	 yppasswd(1),  ypwhich(1),  ypmake(8),
       yppush(8), ypxfr(8)

       Functions: btree(3), dbm(3), dbopen(3), hash(3), ndbm(3), ypclnt(3)

       Files: ypfiles(4)

       Network Administration: Services

								     ypserv(8)
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