Purpose
Enables client
processes to bind, or connect, to an NIS server.
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: - If a domain becomes unbound (usually
when the server crashes or
is overloaded), the ypbind daemon broadcasts again to find
another server.
- To force a client to bind to a specific
server, use the ypset command.
- To find out which server a client is bound to, use the ypwhich command.
- 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.
- 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.
- 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: - 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.
- 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. |