DNS Caching
This page will explain how to install DNS caching to improve DNS lookup performance.
Contents
Install required packages:
Open Synaptic package manager and search for bind. Install below 2 packages.
bind-utils - for dig/nslookup
bind - for DNS caching
Change hostname and domain:
We will set the computername to compname and the domain to somedomain. You can choose any name of your choice for these.
In PCLinuxOS Control Center > Network & Internet > Host definitions add below entries
127.0.0.1 compname.somedomain 127.0.0.1 localhost
You can also add above entries directly to /etc/hosts file. You need to be a root user to edit this file.
Edit file /etc/sysconfig/network as root user and modify below line.
HOSTNAME=compname.somedomain
Start local DNS service:
In PCLinuxOS Control Center > System > "Manage system services..."
Go to named service line, select checkbox next to "on boot", click Start button
Add the new local DNS to network settings:
Add "nameserver 127.0.0.1" without any empty lines to /etc/resolvconf/resolv.conf.d/base
Add below lines to without any empty lines /etc/resolvconf/resolv.conf.d/tail
nameserver 208.67.222.222 nameserver 208.67.220.220
Open a terminal window and change user to root by using su command. Restart network by executing below command
service network resetart
Below is a sample output for the command. Output will vary depending on your network setup.
[root@icsserver andrzejl]# service network restart Shutting down interface eth1: [ OK ] Shutting down interface ppp0: [ OK ] Shutting down loopback interface: [ OK ] Disabling IPv4 packet forwarding: [ OK ] Bringing up loopback interface: [ OK ] Enabling IPv4 packet forwarding [ OK ] Configuring wireless regulatory domain [ OK ] Bringing up interface eth1: [ OK ] Bringing up interface ppp0: [ OK ] [root@icsserver andrzejl]#
Verification of the setup:
Open a terminal window, execute below commands and look for similar output.
[root@icsserver andrzejl]# cat /etc/resolv.conf # Dynamic resolv.conf(5) file for glibc resolver(3) generated by resolvconf( # DO NOT EDIT THIS FILE BY HAND -- YOUR CHANGES WILL BE OVERWRITTEN nameserver 127.0.0.1 nameserver 208.67.222.222 nameserver 208.67.220.220
Below command does a DNS lookup. The first lookup takes 265 msec. The second lookup only takes 1 msec.
[andrzejl@icsserver ~]$ dig pclinuxos.com ; <<>> DiG 9.8.1-P1 <<>> pclinuxos.com ;; global options: +cmd ;; Got answer: ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 10203 ;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 4, ADDITIONAL: 0 ... ;; Query time: 265 msec ... ;; SERVER: 127.0.0.1#53(127.0.0.1) ;; WHEN: Sat Dec 10 21:41:28 2011 ;; MSG SIZE rcvd: 131 [andrzejl@icsserver ~]$ dig pclinuxos.com ; <<>> DiG 9.8.1-P1 <<>> pclinuxos.com ;; global options: +cmd ;; Got answer: ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 8272 ;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 4, ADDITIONAL: 2 ... ;; Query time: 1 msec ... ;; SERVER: 127.0.0.1#53(127.0.0.1) ;; WHEN: Sat Dec 10 21:41:29 2011 ;; MSG SIZE rcvd: 163
