ypbind Daemon

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Purpose

Enables client processes to bind, or connect, to an NIS server.

Syntax

/usr/lib/netsvc/yp/ypbind [ -s -ypset -ypsetme ]

Description

The ypbind daemon binds, or connects, processes on a Network Information Services (NIS) client to services on an NIS server. This daemon, which runs on every NIS client, is started and stopped by the following System Resource Controller (SRC) commands:

startsrc -s ypbind
stopsrc -s ypbind

When a client requests information from a Network Information Services (NIS) map, the ypbind daemon broadcasts on the network for a server. When the server responds, it gives the daemon the Internet address and port number of a host. This is the host that provides the information the client is seeking. The ypbind daemon stores this address information in the /var/yp/binding directory using a file name of domainname.version. Then, the next time the client wants to access an NIS map, the client's ypbind daemon refers to the addresses in the domainname.version file.

The ypbind daemon can maintain bindings to several domains and their servers -ypsetme simultaneously. The default domain is the one specified by the domainname command at startup time.

Note:
  1. If a domain becomes unbound (usually when the server crashes or is overloaded), the ypbind daemon broadcasts again to find another server.
  2. To force a client to bind to a specific server, use the ypset command.
  3. To find out which server a client is bound to, use the ypwhich command.
  4. If the /var/yp/binding/domainname/ypservers file exists, ypbind will attempt to contact the servers listed in that file before broadcasting. The file should contain a list of server IP addresses, one per line.
  5. By default, the NIS client will wait indefinitely for the NIS server, during which time, logins to the client system are not possible. It is possible, however, to limit the length of this wait. If the YPBIND_MAXWAIT environment variable is set (usually in /etc/environment) before the ypbind daemon is started, this value (in seconds) will limit the amount of time the NIS client will wait for the NIS server. If this limit is exceeded, the client behaves as if NIS were unavailable and continues using local files. This will allow local logins, such as root.
  6. If a domain becomes unbound and it is listed in the /var/yp/binding/domainnanme/ypservers file, by default ypbind daemon attempts to contact the server that is currently down; however, if the YPBIND_SKIP environment variable is set to 1 (usually set in the /etc/environment file) before the ypbind daemon is started, the server that is currently down will not be contacted again.

Flags

Item Description
-s Runs the ypbind daemon in a secure mode on privileged communications ports.
-ypset Indicates the local host accepts ypset commands from local or remote hosts.
-ypsetme Indicates that the local host accepts ypset commands only from the local host. This flag overrides the -ypset flag if both are specified.
Note:
  1. If neither the -ypset or -ypsetme flags are specified, the local host rejects all ypset commands from all hosts. This is the most secure mode because the NIS server cannot change.
  2. If neither the -ypset or -ypsetme flags are specified, the local host rejects all ypset commands from all hosts. This is the most secure mode because the NIS server cannot change. However, if no NIS servers exist on the networks directly connected to the client machine, then the -ypsetme flag must be used and the NIS server should be specified with the ypset command.

Files

Item Description
/var/yp/binding directory Contains Internet addresses and port numbers for NIS servers.
/var/yp/binding/domainname/ypservers Contains a list of internet addresses, one per line, of servers to attempt to contact before broadcasting.
domainname.version Binary file that contains the address and port number of the current NIS server.