LPI Linux Certification/Basic DNS Server Configuration

Detailed Objectives (207.1)
(LPIC-2 Version 4.5)

Weight: 3

Description: Candidates should be able to configure BIND to function as a caching-only DNS server. This objective includes the ability to manage a running server and configuring logging.

Key Knowledge Areas:
 * BIND 9.x configuration files, terms and utilities.
 * Defining the location of the BIND zone files in BIND configuration files.
 * Reloading modified configuration and zone files.
 * Awareness of dnsmasq, djbdns and PowerDNS as alternate name servers.

The following is a partial list of the used files, terms and utilities:

Setting up a caching-only nameserver
To speed up the cumbersome process of DNS queries, DNS servers usually cache answers from other DNS servers – even negative queries (i.e an authoritative server's answer « name does not exist » is also cached by your local DNS)

Configuring BIND as a caching-only nameserver involves setting up only a «. » zone, that is, only tell it about the root nameservers and not specifying any zones, as follows :

zone «. » in { type hint; file « named.cache »; };

The file named.cache can be generated by using dig @a.root-servers.net Logging in BIND is controlled by two main concepts : channels and categories A channel specifies where logged data goes : to syslog, to a file, etc... A category specifies what data is logged

Channels allows you to filter messages by priority, like syslog's priorities. They are essentially the same, but two more are available for BIND : debug and dynamic, which affect debug level logging Debug sets a debug level, which will be active after the first trace command is given via ndc; dynamic will increment and decrement debug levels after each trace command is given via ndc

Example of logging configuration:

logging { channel my_syslog { syslog daemon; severity info; }; channel my_file { file « log.msgs »; severity dynamic; }; category statistics { my_syslog; my_file; }; category queries { my_file; }; };

To activate logging, after bind is started, issue a command :

ndc trace

Key terms, files and utilities : /etc/named.conf /usr/sbin/ndc /usr/sbin/named-bootconf Kill