A name server constitutes the server portion of BIND’s client/server mechanism. Resolvers are clients that access the name server. Name servers contain complete information about a particular network segment. Resolvers are library routines that create queries and send them across a network to a name server. A resolver translates a program’s request for host information into a query, sends the query to a name server, and translates the response into an answer. Programs running on a host use a resolver to obtain information about a domain.
A resolver can perform the following functions:
Return the information to the program.
A resolver allows you to configure three aspects of its behavior: the default domain, the search list, and the name servers that the resolver queries.
You can include most of the resolver configurations in the /etc/resolv.conf file. Table 2-2 describes the options in the /etc/resolv.conf file that you can use to configure the resolver’s behavior.
Table 2-2 The /etc/resolv.conf Options
| Option | Description |
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| domain default_domain_name; | The domain option followed by the default domain name.The domain entry is required only when the local system’s host name (as returned by the hostname command) is not a domain name, and the search option is not configured. |
| search domain_name1, domain_name2, domain_name3, domain_name4, domain_name5, domain_name6 | The search option followed by up to six domains separated by spaces or tabs. The first domain in the search list must be the local domain. The resolver appends these domains, one at a time, to a host name that does not end in a dot, when the resolver constructs queries to send to a name server. The domain and search keywords are mutually exclusive. If you do not specify the search option, the default search list contains only the local domain. |
| nameserver Internet_address | The nameserver option followed by the Internet address (in dot notation) of a name server that the resolver must query. You can configure up to three nameserver entries. |
For information on other /etc/resolv.conf option, type man 4 resolv.conf at the HP-UX prompt.
To configure a host to query a name server on a remote host, complete the following steps:
Create a file called /etc/resolv.conf on the host and specify the options domain and nameserver.
The following is an example /etc/resolv.conf file:
domain div.inc.com
nameserver 132.22.0.4
nameserver 132.22.0.12 |
If you do not specify the local domain with the search or domain option, set the default domain name with the hostname command, as shown in the following example:
/usr/bin/hostname indigo.div.inc.com |
Set the HOSTNAME variable in the /etc/rc.config.d/netconf file to the same value, as in the following example:
HOSTNAME=indigo.div.inc.com |
Do not put a trailing dot at the end of the domain name.
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 | NOTE: If you want to run both BIND and HP VUE, you must have an /etc/resolv.conf file on your system, or HP VUE does not start. |
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If you set the LOCALDOMAIN environment variable, any BIND requests made within the context of your shell environment use the search list specified in the LOCALDOMAIN variable. The LOCALDOMAIN variable overrides the domain and search options in /etc/resolv.conf.
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 | CAUTION: In order to avoid situations that may cause connections to unintended destinations, you must carefully select the domains that you put in the search list in the /etc/resolv.conf file. HP recommends that you limit the domains in the search list to the domains administered within your trusted organization. For more information on the security implications of search lists, see RFC 1535 (A Security Problem and Proposed Correction With Widely Deployed DNS Software). |
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For more information, type man 4 resolver or man 5 hostname at the HP-UX prompt, or see “How BIND Resolves Host Names”.
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