HOWTO: Persistant DNS Caching with pdnsd.

[budjo]

I think it's working on my hardy using poopypants step. Moreover, how to set it as dns proxy for networked computer?? It should be possible I guess. Thanks.

[Warren Watts]

I wrote a perl program a while back to analyze the relative speeds of each of the DNS servers detected by dhcpcd (DHCP client daemon) through use of dig (a DNS lookup utility) and display a sorted list of DNS servers from fastest to slowest.

Here's the perl script and the corresponding output from the command line:

#!/usr/bin/perl 

######################################################################################
# scan_dns.pl version 0.7 9/20/07
# Author: Warren Watts (kingbeetle_66(at)yahoo(dot)com

# This program will analyze the relative speeds of each of the DNS servers
# detected by dhcpcd (DHCP client daemon) through use of dig (a DNS lookup utility)
# and display a sorted list of DNS servers from fastest to slowest.
# This sorted list can then be used to tweak the /etc/resolv.conf file, providing
# faster DNS lookups while browsing, etc.
 
# I included three domains for dig to lookup.  They are stored in @domain_list.
# Feel free to add to the list or change the domain list to any domains you wish.
# Be aware that the more domains in the list, the longer the scan will take!
#######################################################################################

use strict;

my (@DNS,$IP,$time,$domain,$dig,%time,$key);

# Read the DNS list from /etc/resolv.conf and store the list in an array
my $resolv = `cat /etc/resolv.conf`;
while ($resolv =~ /nameserver (.*)\n/g) {push(@DNS,$1)}

#List the DNS servers listed in /etc.resolv.conf
print "+----------------------------------------------------------------------+\n";
print "The following DNS servers are listed in /etc/resolv.conf:\n";
foreach $IP (@DNS) {print "$IP\t"}
print "\n";

# Store list of domains to be looked up by dig in an array
my @domain_list = ('www.yahoo.com' ,'www.fasthit.net' ,'zz.nullwave.ru');

# List the domains to be used by dig during the scan
print "The following domains will be for this scan:\n";
foreach $domain (@domain_list) {print "$domain\t"}
print "\n";
print "+----------------------------------------------------------------------+\n";

# Count number of domains stored in the array
my $domain_count = @domain_list; 
# Go through the list of DNS servers and execute dig for each DNS server and each  
# domains in the domain list, extract the time taken and average the times together,
# then store the DNS and averaged time in a hash.
foreach $IP (@DNS) 
{
  print "Scanning $IP\n";
  $time = '';
  foreach $domain (@domain_list)
  {
    print "-->  $domain\n";
    $dig = `dig \@$IP $domain`;
    if ($dig =~ /Query time: (.*) msec/) 
    {
      $time = $time + $1;
    }
  }
  $time{$IP} = int(($time / $domain_count) +0.5);
}
print "+----------------------------------------------------------------------+\n";

# Display the results sorted by time in ascending order
foreach my $key (sort hashValueAscendingNum (keys(%time))) 
 {
  print "Average fetch time for $key : $time{$key}\n";
}

# Subroutine to sort by time rather than by DNS address
sub hashValueAscendingNum 
{
   $time{$a} <=> $time{$b}
}

Sample output:

everyone@ubuntu550:~/Desktop$ perl test.pl
+----------------------------------------------------------------------+
The following DNS servers are listed in /etc/resolv.conf:
208.67.222.222 208.67.220.220 192.168.0.1
The following domains will be for this scan:
www.yahoo.com www.fasthit.net zz.nullwave.ru
+----------------------------------------------------------------------+
Scanning 208.67.222.222
--> www.yahoo.com
--> www.fasthit.net
--> zz.nullwave.ru
Scanning 208.67.220.220
--> www.yahoo.com
--> www.fasthit.net
--> zz.nullwave.ru
Scanning 192.168.0.1
--> www.yahoo.com
--> www.fasthit.net
--> zz.nullwave.ru
+----------------------------------------------------------------------+
Average fetch time for 208.67.222.222 : 43
Average fetch time for 208.67.220.220 : 291
Average fetch time for 192.168.0.1 : 834

You should be able to use this to test whether your local DNS cache is working, right?

I also included the script as a handy tarball as well.

[jonthysell]

This is all I did in Jaunty, without any config file editing.

Quick Summary:

sudo cp /etc/resolv.conf /etc/resolv.conf.bak
sudo apt-get install resolvconf
sudo apt-get install pdnsd

Choose "Use resolvconf". In the next line, replace eth0 with the name of your interface if it's different.

sudo mv /etc/resolv.conf.bak /etc/resolvconf/run/interface/eth0
sudo resolvconf -u

Done! If you want step-by-step explanations:

Longer Steps:

First, save your current nameserver setup (this is not superfluous paranoia, you're going to need this later):

sudo cp /etc/resolv.conf /etc/resolv.conf.bak

Next install resolvconf. If we don't install it first, we'll get weird errors from pdnsd because of how resolvconf replaces the /etc/resolv.conf file with a symbolic link:

sudo apt-get install resolvconf

Next install pdnsd:

sudo apt-get install pdnsd

Choose "Use resolvconf".

You'd assume that it would just work, but it doesn't, cause the setup process has lost your original nameserver information.

So when you try to resolve a name, the system will look to resolvconf, who'll direct the request to pdnsd. Pdns has nothing cached yet, so it asks resolvconf for the next server to check, but resolvconf has no one to ask next.

So, we tell resolvconf that for that network interface, to use the config we were using before we started any of this. So move the backup file we made where resolvconf can see it. Since this was for my eth0 interface, I used:

sudo mv /etc/resolv.conf.bak /etc/resolvconf/run/interface/eth0

Finally, update resolvconf with:

sudo resolvconf -u

Took me a few tries to pare this down, but this works for me, end to end.

For a wireless config (where you're connecting to different networks), or if you just want to use say, OpenDNS for all of your interfaces all the time, just create a file /etc/resolvconf/run/interface/opendns with the following:

nameserver 208.67.222.222
nameserver 208.67.220.220

Then update resolvconf again with:

sudo resolvconf -u

Hope this helps!

[noren]

wow it worked from the help of above post real short and simple

[djkmmo]

Hi, I got the same problem. Everything needs 0 ms to llokup even with ones I tried the first time. Ridiculous! I really want to use this tool. Can anyone offer help?

A bit late, but I haven't used this tool before. I run 8.04 and had the same problem as you and this solved it for me: pdnsd doesn't honor the settings in /etc/pdnsd.conf if AUTO_MODE is set in /etc/default/pdnsd and it is set to resolveconf by default. I.e. you can change whatever you want in /etc/pdnsd.conf and it will have no effect whatsoever.

The solution is to comment out AUTO_MODE in /etc/default/pdnsd, then /etc/pdnsd.conf will be used insted of /usr/share/pdnsd/pdnsd-$AUTO_MODE.conf (/usr/share/pdnsd/pdnsd-resolvconf.conf in most cases). You shouldn't edit /usr/share/pdnsd/pdnsd-$AUTO_MODE.conf directly as this file probably will be replaced when the package is upgraded.

If you want to see if it's actually caching anything you can do a lookup in the cache with pdnsd-ctl dump before and after you have done a dig:

USER @ Computer:~$ sudo pdnsd-ctl dump |grep -i google.com
[1] USER @ COMPUTER:~$ dig  @localhost google.com mx
...
USER @ Computer:~$ sudo pdnsd-ctl dump |grep -i google.com
google.com.

Replace "google.com" with an address you haven't visited. The "[1]" after the first command means that grep couldn't find any hits for the string from the output of pdnsd-ctl dump.

[noren]

is there any way to use ad-block list with pdsd

[gillespiea]

I'd just like to say a big thank you.
I was wondering why my internet wasn't loading as fast as it did when i used windows, then i stumbled on this. thanks soooo much. My internet is now stupidly fast again

[Artemis3]

I'm even lazier so avoided resolvconf by using the magical command:

sudo apt-get --no-install-recommends install pdnsd

And followed instructions exactly like the first post

[allstats]

I'm even lazier so avoided resolvconf by using the magical command:

sudo apt-get --no-install-recommends install pdnsd

And followed instructions exactly like the first post

Thats it. Me too. Grate effect on my netbook.

[corruptor1972]

FYI there is a bug registered on Launchpad: pdnsd requires manual restart after new WiFi connection gets established.

I was having all sorts of problems with this issue and (eventually) came up with the solution I posted there.

I installed pdnsd and resolvconf and chose the Manual setup when prompted.