nisprefadm(1M)						  System Administration Commands					    nisprefadm(1M)

NAME

       nisprefadm - NIS+ utility to set server preferences for NIS+ clients

SYNOPSIS

       /usr/bin/nisprefadm -a {-L | -G} [-o opt-string]
	    [-d domain] [-C client] server...

       /usr/bin/nisprefadm -m {-L | -G} [-o opt-string]
	    [-d domain] [-C client] oldserver=newserver...

       /usr/bin/nisprefadm -r {-L | -G} [-o opt-string]
	    [-d domain] [-C client] server...

       /usr/bin/nisprefadm -u {-L | -G} [-o opt-string]
	    [-d domain] [-C client] server...

       /usr/bin/nisprefadm -x {-L | -G} [-d domain] [-C client]

       /usr/bin/nisprefadm -l {-L | -G} [-d domain] [-C client]

       /usr/bin/nisprefadm -F

DESCRIPTION

       nisprefadm  defines which servers are to be preferred by NIS+ clients. This information is used by nis_cachemgr(1M) to control the order in
       which it selects which server to use for a particular domain. On a client system, the cache manager  first  looks  for  a  local  preferred
       server list in /var/nis. If it doesn't find one, it looks for an entry with its host name in the NIS+ table. Finally, if it doesn't find it
       there, it looks for an entry for its subnet.

       By default, nis_cachemgr puts all servers that are on the same subnet as the client system (that is, local servers) are	on  the  preferred
       server  list.  In  some cases this default preferred server list is inadequate. For example, if all of the servers for a domain are remote,
       but some are closer than others, the cache manager should try to select the closer one. Because the cache manager has no  reliable  way	to
       determine the distance to remote servers, nisprefadm is used to provide this information.

       The  preferred server information is stored either globally in a NIS+ table (with the -G option) or locally in a file, /var/nis/client_info
       (with the -L option). It is preferable to store the information globally so  that  it  can  be  used  by  all  clients  on  a  subnet.  The
       nis_cachemgr  process  on  a client machine reloads the preferred server information periodically, depending on the machine's setup. If the
       local file is used, the information is reloaded every 12 hours. If the global table is used, the information is reloaded based on  the  TTL
       value  of  the  client information table. This TTL value can be changed using  nischttl(1). If you want your changes to take effect immedi-
       ately, use the nisprefadm -F command. When changing local information (-L), nisprefadm automatically  forces  nis_cachemgr  to  reload  the
       information.

       The cache manager assigns weights to all of the servers on the preferred list. By default, local servers (that is, servers on the same sub-
       net) are given a weight of 0. Other servers are given the weight, "infinite". This can be changed by using the nisprefadm command and  giv-
       ing  a  weight  in  parentheses	after  the server name. When selecting a server for a domain, the cache manager first tries to contact the
       servers with the lowest weight. If it doesn't get a response, it tries the servers with the next lowest weight, and so on. If it  fails	to
       get a response from any of the preferred servers, it tries to contact the non-preferred servers.

       The  use  of  weights  gives  fine  control over the server selection process, but care must be given to avoid assigning too many different
       weights. For example, if weights 0, 1, 2, and 3 are used, but all of the servers with weight 0, 1, and 2, are unavailable, then there  will
       be  a  noticeable delay in selecting a server. This is because the cache manager waits 5 seconds for a response at each weight level before
       moving on to the next one. As a general rule, one or two weight levels provides a good balance of server selection control and performance.

       When specifying a server name, it is not necessary to fully qualify the name. When the cache manager tries to access a domain, it  compares
       the  list  of servers for the domain with the list of preferred servers. It will find a match if a preferred server name is a prefix of the
       name of a server for the domain. If a domain is served by two servers with the same prefix, the preferred server name must  include  enough
       of the domain name to distinguish the two.

       The  nis_cachemgr(1M) process automatically adds local servers (same subnet as the client) to the preferred server list with a weight of 0.
       Thus, it is not necessary to specify them, though it does no harm.

       If you specify a weight for a server, you probably should quote the parentheses to avoid having the shell  interpret  them.  The  following
       command illustrates this:

	 example% nisprefadm -G -a -C client1 "srv1(2)"

       In general, nis_cachemgr does a fairly good job of selecting servers on its own. Therefore, the use of nisprefadm is not usually necessary.
       Some situations in which it is recommended are:

       No local servers, many remote servers

	   In this case, nis_cachemgr needs to choose one of the remote servers. Because it doesn't have information on which is closest, it sends
	   a  ping  to	all  of  them  and  then selects the one that responds fastest. This may not always select the best server. If some of the
	   servers are closer to the client than the others, they should be listed as preferred servers so that nis_cachemgr will try them  first.
	   This reduces the amount of network traffic for selecting a server.

       Very remote servers

	   In  some  networks  there  are  NIS+ servers that are only reachable through very slow network connections. It is usually best to avoid
	   unnecessary traffic over that connection. If the pref_type=pref_only option is set along with preferred servers,  then  only  the  pre-
	   ferred  servers  are  contacted  for  domains  they serve. The non-preferred servers are not tried at all; even if all of the preferred
	   servers are unavailable. For domains that are not served by any of the preferred servers, the pref_only option is ignored.

OPTIONS

       In the SYNOPSIS, when several options are surrounded by braces (that is, by `{' and `}') one of the options must be specified.

       -a	    Add the specified servers to the preferred server list.

       -C client    Store the preferred server information with the key, client. The client can be either a hostname or a subnet  number.  When  a
		    hostname  is  specified, the preferred server information applies to that host only. When a subnet is specified, the preferred
		    server information applies to all clients on that subnet. The cache manager searches for host specific entries first. It  only
		    searches  for  subnet  entries if no host entry is found. If this option is not specified, then the hostname of the machine on
		    which the command is run is used.

       -d domain    Specify the domain to which the command is to apply.

       -F	    Tells nis_cachemgr(1M) to refresh its preferred server information. The program periodically does this anyway, but this option
		    forces  it	to  do the refresh immediately. When updating the local information, nis_cachemgr automatically refreshes the pre-
		    ferred server information.

		    This option must be executed as root.

       -l	    List the current preferred server information.

       -L | -G	    Store the preferred server information locally in the file, /var/nis/client_info (the -L option), or globally in a NIS+  table
		    client.info.org-dir.domain	(the -G option). If the information is stored locally, then it only applies to the system on which
		    the command is run. If it is stored globally then it can apply to all systems on a subnet (depending on the value  of  the	-C
		    option).

		    The -L option must be run as root.

       -m	    Modify the preferred server list. The server specified by oldserver is replaced by newserver. This is typically used to change
		    the weight for a server.

       -o	    Specify additional options to control server selection. Currently the only valid option is pref_type, which can have  a  value
		    of	either	all (the default) or pref_only. If the value is all, then the cache manager tries to contact non-preferred servers
		    if all of the preferred servers fail to respond. If pref_only is specified, then it won't try non-preferred servers. The  only
		    exception  to this is when a domain is not served by any of the preferred servers. In this case, the cache manager ignores the
		    option. This is to avoid requiring that preferred servers be defined for every domain.

       -r	    Remove the specified servers from the preferred server list.

       -u	    Clear the list of preferred servers and then add the specified servers to the preferred server list.

       -x	    Remove the preferred server information completely.

RETURN VALUES

       nisprefadm returns the following values:

       0    On success.

       1    On failure.

EXAMPLES

       Example 1 Using nisprefadm

       This command sets the preferred server list for the system on which it is run:

	 example% nisprefadm -L -a srv1 srv2

       The information is stored in a file, /var/nis/client_info, so it will only affect this one system.

       The following command has the same effect, but the information is stored in a NIS+ table in the default domain.

	 example% nisprefadm -G -a srv1 srv2

       As a system administrator, you might want to set the preferred server information for a client system other than the one  you  are  running
       the command on. The following command sets the preferred server information for a client system named client1:

	 example% nisprefadm -G -a -C client1 srv1 srv2

       It  is  common  for  all client systems on a subnet to use the same set of preferred servers. The following command sets a preferred server
       list that applies to all clients on subnet, 192.85.18.0:

	 example% nisprefadm -G -a -C 192.85.18.0 srv1 srv2

ATTRIBUTES

       See attributes(5) for descriptions of the following attributes:

       +-----------------------------+-----------------------------+
       |      ATTRIBUTE TYPE	     |	    ATTRIBUTE VALUE	   |
       +-----------------------------+-----------------------------+
       |Availability		     |SUNWcsu			   |
       +-----------------------------+-----------------------------+

SEE ALSO

       nischttl(1), nis_cachemgr(1M), attributes(5)

NOTES

       NIS+ might not be supported in future releases of the Solaris Operating system. Tools to aid the migration from NIS+ to LDAP are  available
       in the current Solaris release. For more information, visit http://www.sun.com/directory/nisplus/transition.html.

SunOS 5.11							    12 Dec 2001 						    nisprefadm(1M)