Chapter 5 Configuring the Name Service Switch

The Name Service Switch determines where your host will look for the information that is traditionally stored in the following files:

You can configure your host to look for each type of information in NIS or the local /etc file. You can configure your host to consult either or both of these sources, in any order.

For host information (host names and IP addresses), you can configure your host to consult BIND (DNS) in addition to NIS or the local /etc/hosts file.

The default Name Service Switch configuration is adequate for most installations, so you probably do not have to change it. The default configuration is explained in “Default Configuration”.

The ability to consult more than one name service for host information is often called hostname fallback. The Name Service Switch provides client-side hostname fallback, because it is used by client-side programs (for example, gethostbyname), which request host information.

NIS allows you to configure a server-side hostname fallback, which causes the NIS server to query BIND when it fails to find requested host information in its database. The NIS server then returns the host information to the client through NIS. This server-side hostname fallback is intended for use with clients like PCs that do not have a feature like the Name Service Switch. Hewlett-Packard recommends that you use the Name Service Switch if possible, instead of the server-side hostname fallback provided by NIS. For more information on the NIS server-side hostname fallback, see “To Query BIND for Host Information After Querying NIS”.

You can use SAM to configure the Name Service Switch. Type sam at the HP-UX prompt.

This chapter tells you how to configure the Name Service Switch. It contains the following sections:

	NOTE: Configuring the Name Service Switch is a separate task from configuring the name services themselves. You must also configure the name services before you can use them. The Name Service Switch just determines which name services are queried and in what order.