THIS IS A TEST INSTANCE. ALL YOUR CHANGES WILL BE LOST!!!!
Caching Nameserver
Often SpamAssassin users will find that their system is performing many DNS (Domain Name System) lookups. There are many NetworkTests in the suite of tests. The network tests significantly enhance the ability of SpamAssassin to correctly catagorize messages. One of the main network tests is to look up domain names in the DnsBlocklists.
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The standard solution is to install a local caching nameserver to cache repeated DNS requests. This will significantly reduce network traffic due to DNS lookups. This improves system efficiency.
Installing BIND As A Caching Nameserver
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This section describes installing \[http://www.isc.org BIND\] (Berkeley Internet Name Daemon) in a caching configuration on the system. BIND is the standard nameserver in use on the Internet today. More internet servers run BIND than any other nameserver daemon. Several alternative DNS nameservers in common use are described in their own sections below. |
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yum install caching-nameserver chkconfig named on service named start |
Installing djbdns As A Caching Nameserver
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\[http://cr.yp.to/djbdns.html djbdns\] / \[http://tinydns.org/ tinydns\] is D. J. Bernstein's DNS daemon. |
If you have a good guide to the commands required to install this on a typical system, please edit this page and fill out this section.
Installing rbldnsd As A Caching Nameserver
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\[http://www.corpit.ru/mjt/rbldnsd.html rbldnsd\] is a small and fast DNS daemon which is especially made to serve DNSBL zones. This daemon was inspired by Dan J. Bernstein's rbldns program found in the djbdns package. The \[http://www.surbl.org/dnscache-rbldnsd.html rbldnsd FAQ\] at surbl.org. |
If you have a good guide to the commands required to install this on a typical system, please edit this page and fill out this section.
Installing dnsmasq As A Caching Nameserver
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\[http://thekelleys.org.uk/dnsmasq/doc.html dnsmasq\] is a small DNS server (also includes a lightweight DHCP server). |
If you have a good guide to the commands required to install this on a typical system, please edit this page and fill out this section.
Setting up the system to use the Caching Nameserver
GNU C library configuration
For the current glibc version 6 the host lookup ordering is configured in the /etc/nsswitch.conf file. The typical configuration would specify the local system file first and the network DNS database second.
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order hosts,bind |
/etc/resolv.conf
The /etc/resolv.conf file configures the nameserver used to look up DNS data. A typical system contains a search line to specify the local domain. It also contains up to three nameserver lines to configure nameservers. Because we are setting up a local caching nameserver only one entry is needed. The 0.0.0.0 entry specifies that the nameserver on the local host will be contacted for DNS lookups.
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Note that if your host uses a client configuration with DHCP to configure networking that this file may be overwritten by the DHCP client on the local host every time the network is enabled. See your DHCP documentation for more information.
/etc/hosts
The /etc/hosts file is the original location for DNS data. However it is not used generally for DNS lookups on modern systems. It is impossible to keep the entire Internet database there. But it is still used for a small amount of local system data.
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