ypserv(8yp)ypserv(8yp)Name
ypserv, ypbind - yellow pages server and binder processes
Syntax
/usr/etc/ypserv [-l]
/etc/ypbind [-S]domainname, servername,...
Description
The yellow pages (YP) service provides a simple network lookup service
consisting of databases and processes. The databases are files in a
directory tree rooted at These files are described in The processes are
the YP database lookup server, and the YP binder. The programmatic
interface to YP is described in Administrative tools are described in
and Tools you can use to view the contents of YP maps are described in
and Database generation and maintenance tools are described in and
Both and are daemon processes typically activated at system startup
time from The command runs only on a YP server machine with a complete
YP database. The command runs on all machines using YP services; that
is, YP servers and clients.
The daemon's primary function is to look up information in its local
database of YP maps. The operations are defined for the programmer in
the header file
Communication with is by means of RPC calls. Lookup functions are
described in and are supplied as C-callable functions in
There are four lookup functions, which are performed on a specified map
within some YP domain: and The operation takes a key and returns the
associated value. The operation returns the first key-value pair from
the map, and the operation returns the remaining key-value pairs. The
operation ships the entire map to the requester.
The and functions supply information about the map, rather than the map
entries. Both the order number and the master name exist in the map as
key-value pairs, but the server does not return either through the nor‐
mal lookup functions. (If the map is examined with however, they are
visible.)
Other functions are used within the YP subsystem itself, and are not of
general interest to YP clients. They include: the the and the func‐
tions.
The purpose of the daemon is to store information that lets client pro‐
cesses on a single node communicate with a process. The function must
run on every machine that has YP client service requirements. The
function must be started through an entry in the file.
The -l option toggles log messages. When toggled on, the messages are
logged to the file. Related messages are logged to the file. Any
fatal errors, such as not being able to open the file, or access
denials, are logged to
The option allows the system administrator to lock to a particular
domain and set of servers. Up to four servers can be specified. The
function may or may not be running on the same node, but must be run‐
ning somewhere on the network. The servers with the option must have
entries in the local file.
The information stores is called a which is the association of a domain
name with the internet address of the YP server and the port on that
host at which the 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 process broadcasts on the net trying to
find a process that serves maps within that domain. Because the bind‐
ing is established by broadcasting, there must be at least one process
on every net. Once a domain is bound by a particular that same binding
is given to every client process on the node. The process on the local
node or a remote node may be queried for the binding of a particular
domain by using the command.
Bindings are verified before they are given out to a client process.
If is unable to communicate with the process to which it is bound, 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 fail immediately. In general, a bound domain is
marked as unbound when the node running crashes or gets overloaded.
When the node gets overloaded, tries to bind any YP server (typically
one that is less-heavily loaded) available on the net.
The process also accepts requests to set its binding for a particular
domain. The request is usually generated by the YP subsystem itself.
Notes
If the file exists when starts up, log information is written to when
error conditions occur.
Files
Specifies which YP clients are permitted to request maps
See Alsoypserv(8yp)
