DNS caching

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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
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