ypserv is a fundamental part of the network information system called NIS. This server provides information from NIS maps to the NIS clients on the network.
A NIS map is stored on the server as a
db(3) database. A number of NIS maps is grouped together in a domain.
ypserv determines the domains it serves by looking for a directory with the domain name in
/var/yp.
In an effort to improve the security of NIS (which has, historically, not been very good), this
ypserv has support for libwrap-based access control. See
hosts_access(5) for more information. The
daemon used for access control is the name which
ypserv was invoked as (typically “ypserv” ). If a host is not allowed to query this NIS server,
ypserv will return the NIS result code YP_NODOM. To avoid problems with DNS lookups causing
ypserv to hang,
ypserv disables DNS lookups for its client
hosts_access(5) lists. The result is that
ypserv can only use address based patterns. This also means that wildcard patterns such as LOCAL or KNOWN will not work.
The process pid of the
ypserv process can be found in the file
/var/run/ypserv.pid.
The options are as follows:
-d
Use internet Domain Name System. If a query to map hosts.byname or hosts.byaddr fails, make a DNS query and return the result if successful.
-f
Run in the foreground.
-l
Enable logging of all requests.
-p port
Bind to the specified port instead of dynamically allocating one.
All messages are sent to the system log with the facility LOG_DAEMON. Error messages have the priority LOG_ERR. Refused requests are logged with the priority LOG_WARNING. All other messages are logged with the priority LOG_INFO.