ypserv(1M)

DESCRIPTION

The Network Information Service (NIS) provides a simple network lookup service consisting of databases and processes. The databases are files in a directory tree rooted at /var/yp (see ypfiles(4)). The processes are /usr/lib/netsvc/yp/ypserv, the NIS database lookup server, and /usr/lib/netsvc/yp/ypbind, the NIS binder. Both ypserv and ypbind are daemon processes activated at system startup time when the NIS_MASTER_SERVER or NIS_SLAVE_SERVER variable is set to 1, for ypserv, and the NIS_CLIENT variable is set to 1, for ypbind, in the /etc/rc.config.d/namesvrs file.

The NIS programmatic interface is described in ypclnt(3C). Administrative tools are described in ypwhich(1), yppoll(1M), yppush(1M), ypset(1M) and ypxfr(1M). Tools to see the contents of NIS maps (databases) are described in ypcat(1) and ypmatch(1). Database generation and maintenance tools are described in makedbm(1M), ypinit(1M), and ypmake(1M). The command to set or show the default NIS domain is domainname(1).

ypxfrd transfers entire NIS maps in an efficient manner. For systems that use this daemon, map transfers will be faster, depending on the map. ypxfrd should be run on a server running HP-UX release 10.0. ypxfr (see ypxfr(1M)) will attempt to use ypxfrd first. If that fails, it will use the older transfer method. The ypxfrd daemon is activated at system startup time when the NIS_MASTER_SERVER or NIS_SLAVE_SERVER variable is set to 1 in the /etc/rc.config.d/namesvrs file.

The ypserv daemon's primary function is to look up information in its local collection of NIS maps. It runs only on NIS server machines providing data from NIS databases. Communication to and from ypserv is by means of RPC. Lookup functions are described in ypclnt(3C).

Four lookup functions perform on a specific map within a NIS domain: Match, Get_first, Get_next, and Get_all. The Match operation matches a key to a record in the database and returns its associated value. The Get_first operation returns the first key-value pair (record) from the map, and Get_next enumerates (sequentially retrieves) the remainder of the records. Get_all returns all records in the map to the requester as the response to a single RPC request.

Two other functions supply information about the map other than normal map entries: Get_order_number and Get_master_name. The order number is the time of last modification of a map. The master name is the host name of the machine on which the master map is stored. Both order number and master name exist in the map as special key-value pairs, but the server does not return these through the normal lookup functions. (If you examine the map with makedbm or yppoll (see makedbm(1M) or yppoll(1M)), they will be visible.) Other functions are used within the NIS system and are not of general interest to NIS clients. They include:

The ypbind daemon remembers information that lets client processes on its machine communicate with a ypserv process. The ypbind daemon must run on every machine using NIS services, both NIS servers and clients. The ypserv daemon may or may not be running on a NIS client machine, but it must be running somewhere on the network or be available through a gateway.

The information that ypbind remembers is called a binding: the association of a NIS 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. This information is cached in the directory /var/yp/binding using a filename in the form domainname.version.

Client requests drive the binding process. As a request for an unbound domain comes in, the ypbind process broadcasts on the network, if the file /var/yp/binding/domain_name/ypservers does not exist, trying to find a ypserv process serving maps within that NIS domain. If the binding should be established by broadcasting, at least one ypserv process must exist on every network. If the file /var/yp/binding/domain_name/ypservers is present, then ypbind will try to bind to one of the NIS servers in the order of its listing in the file. If ypbind was unable to bind to any one of the servers available in the list, it will try establishing a binding by broadcasting. The file, /var/yp/binding/domain_name/ypservers, containing the list of NIS servers is created by invoking ypinit with -c option. (see ypinit(1M)). If ypbind is invoked with a -broadcast option, ypbind will try to establish a binding by broadcast immaterial of the availability of the file /var/yp/binding/domain_name/ypservers i.e. the option -broadcast overrides the existence of the file /var/yp/binding/domain_name/ypservers. Once a binding is established for a client, it is given to subsequent client requests. Execute ypwhich to query the ypbind process (local and remote) for its current binding (see ypwhich(1)).

Bindings are verified before they are given to a client process. If ypbind is unable to transact with 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 again. Requests received for an unbound domain fail immediately. Generally, a bound domain is marked as unbound when the node running ypserv crashes or is overloaded. In such a case, ypbind binds to any NIS server (typically one that is less heavily loaded) that is available on the network.

The ypbind daemon also accepts requests to set its binding for a particular domain. ypset accesses the Set_domain facility; it is for unsnarling messes and is not for casual use.

AUTHOR

ypserv, ypbind, and ypxfrd were developed by Sun Microsystems, Inc.

FILES

SEE ALSO

domainname(1), ypcat(1), ypmatch(1), yppasswd(1), ypwhich(1), makedbm(1M), rpcinfo(1M), ypinit(1M), ypmake(1M), yppasswdd(1M), yppoll(1M), yppush(1M), ypset(1M), ypxfr(1M), ypclnt(3C), yppasswd(3N), ypfiles(4).