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<title>Speeding Up Your Net Browsing with PDNSD Domain Name Caching LG #65</title>
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<H1><font color="maroon">Speeding Up Your Net Browsing with PDNSD Domain Name Caching</font></H1>
<H4>By <a href="mailto:sunil_tt@yahoo.com">Sunil Thomas Thonikuzhiyil</a></H4>
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<P> <HR> <P>
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<p>1. Where to find this document
<br>2. About PDNSD
<br>3. Installation
<br>4. Sample configuration file
<br>5. Tweaking configuration files
<br>6. FAQs
<br>7. Credits
<h2>
1. Where to find this document</h2>
<p><br><a href="http://geocities.com/sunil_tt/pdnsd.txt">http://geocities.com/sunil_tt/pdnsd.txt</a>
<h2>
2. About PDNSD.</h2>
DNS is is the Domain Name System. DNS converts machine names to the IP
addresses that all machines on the net have. Name serving on Unix is commonly
done by a program called named. This is a part of the ``BIND'' package
which is coordinated by Paul Vixie for The Internet Software Consortium.
<p>PDNSD is a caching DNS proxy server. Unlike BIND, it saves the RAM cache
to a file and the same is read up by PDNSD for the next Dial-Up session.
BIND when acting as a cacheing nameserver on your local Dial-Up machine
stores/caches the name to number translation data in your RAM. This is
not written back to the hard-disk upon disconnection 'coz it is not intended
for a user/site who/which is not always connected to the Net.
<p>PDNSD can be configured to speed up Net Surfing on a Dial-Up connection.
Since DNS resolution is referenced from the cached file, time is not wasted
on the name to number lookup. This in turn speeds up the name to number
translation, which actually accelerates your surfing.
<p>PDNSD is distributed under the GNU/GPL and is available for download
at: <A HREF="http://home.t-online.de/home/Moestl/">http://home.t-online.de/home/Moestl/</A>
<p>Redhat RPMS are at:
<p><a href="http://home.t-online.de/home/Moestl/">http://home.t-online.de/home/Moestl/</a>
<p>Debian DEBS are at:
<p><a href="ftp://ftp.debian.org/debian/pool/main/p/pdnsd/pdnsd_1.1.2.a-2_i386.deb">ftp://ftp.debian.org/debian/pool/main/p/pdnsd/pdnsd_1.1.2.a-2_i386.deb</a>
<h2>
3. Installation.</h2>
Download pdnsd-&lt;version&gt;.tar.gz from the above source.
<p>Decompress and untar using
<pre>tar zxvf pdnsd-&lt;version&gt;.tar.gz</pre>
Change directory to pdnsd-&lt;version&gt; and type
<pre>$ ./configure</pre>
Configure script accepts a number of parameters, see manual.txt file supplied
with the PDNSD source. Command line parameters --prefix and --with-distribution
are interesting.
<pre>$ ./configure --help</pre>
will list all options
<p>I am assuming that you have not specified any command line options.
Makefile generated by configure will have the following defaults:
(It is worth taking a look at the generated Makefile)
<p>Default installion directory for PDNSD is /usr/local (can be changed
with --prefix option to configure).
Default location of the PDNSD cache is /var/cache/pdnsd.
PDNSD configuration file pdnsd.conf will be found in /etc.
<p>Now type:
<pre>$ make</pre>
This will compile pdnsd. I did not face any problem compiling it on both
Debian 2.2 and Redhat 6.1. Next su to root, as installation requires root
previleges. Then type:
<pre># make install</pre>
This step will do the following (quoted from pdnsd manual.txt):
<OL>
<LI>Copies pdnsd to $(prefix)/sbin/ <P>
<LI>Copies pdnsd-ctl to $(prefix)/sbin/ <P>
<LI>Copies docs/pdnsd.conf (a sample configuration) to /etc/ (and backs
up /etc/pdnsd.conf to /etc/pdnsd.conf.old). If you have an /etc/pdnsd.conf.old
you do not want to be overwritten, save it to another place/name before
doing 'make install' <P>
<LI>Creates your cache directory if it is not there. After installation,
you should check the file permissions and edit /etc/pdnsd.conf to fit your
needs . If you use the run_as option, please make sure that your cache
directory is owned by the user you specified with this option! Please note
that the permission issue has been fixed as of the latest releases. Now
/usr/local/sbin will contain two binaries pdnsd and pdnsd-ctl. 'pdnsd'
is the proxy DNS daemon and 'pdnsd-ctl' is a program to control the cache. <P>
</OL>
<p>The cache is located at /var/cache/pdnsd/pdnsd.cache.The cache file
size will be 4 initially and will grow as and when you browse.This aspect
of the /etc/pdnsd.conf viz. 'perm_cache=&lt;value&gt;;'. By default it is
set as 512(KB).Increase it according to your judgement and a safe value
would be 2048(KB) for a machine having 64MB RAM. The cache file size will
be 4 bytes initially and will grow as and when you browse. Cache growth will be
observed only after a reboot or after restart of the PDNSD daemon. This is due to the fact that PDNSD saves the RAM cache upon exit only.
<p>PDNSD must be started up each time you boot the system . For this, you
have to install start up scripts. rc folder of the source distribution
contains startup scripts for Redhat, SuSE and Debian. I have not tested
the SuSE scripts.
<p>Do the following depending on your distribution.
<h3>
3.a) Debian GNU/Linux.</h3>
Copy pdnsd-{version}/src/rc/Debian/pdnsd to /etc/init.d and type update-rc.d
Stop bind if you have it installed on your system. Edit /etc/resolv.conf
and add the following.
<pre>
nameserver 127.0.0.1
</pre>
<p>Comment out entries for all other name servers. Start pdnsd by typing
/etc/init.d/pdnsd start. Test pdnsd by typing nslookup. On my system it
diplays:
<pre>
Default Server: debian
Address: 127.0.0.1
&gt;
</pre>
<p>Stop pdnsd by typing /etc/init.d/pdnsd stop.
<br>Fire up your editor and add a line like this to the end of your /etc/hosts
file:
<pre>
127.0.0.2 testhost
</pre>
<p>Save the file and start pdnsd once again. Type nslookup. Inside nslookup
type 'testhost'.
<pre>
&gt; testhost
Server: debian
Address: 127.0.0.1
Non-authoritative answer:
Name: testhost
Address: 127.0.0.2
</pre>
If this answer is obtained it shows that your pdnsd is working (remember
to remove the last line from /etc/hosts)
<h3>
3.b) Redhat Linux</h3>
<p><br>Copy pdnsd-{version}/src/rc/Redhat/pdnsd to /etc/rc.d/init.d Stop
bind if you have it installed on your system. Edit /etc/resolv.conf and
add the following
<pre>
nameserver 127.0.0.1
</pre>
<p>Comment out entries for all other name servers. Start pdnsd by typing
/etc/rc.d/init.d/pdnsd start. Test pdnsd by typing nslookup. On my system
it diplays
<pre>
Default Server: Redhat
Address: 127.0.0.1
&gt;
</pre>
<p>Stop pdnsd by typing /etc/rc.d/init.d/pdnsd stop.
<br>Fire up your editor and add a line like this to the end of your /etc/hosts
file.
<pre>
127.0.0.2 testhost
</pre>
<p>Save the file and again start pdnsd. Type nslookup. Inside nslookup
type 'testhost'.
<pre>
&gt; testhost
Server: Redhat
Address: 127.0.0.1
Non-authoritative answer:
Name: testhost
Address: 127.0.0.2
</pre>
<p>If this answer is obtained it shows that your pdnsd is working (remember
to remove the last line from /etc/hosts)
<h2>
4. Sample configuration file.</h2>
My pdnsd.conf looks like this
<HR NOSHADE>
<pre>
global {
perm_cache=2048;
cache_dir="/var/cache/pdnsd";
max_ttl=204800;
run_as="nobody";
paranoid=on;
server_port=53;
server_ip="127.0.0.1";
}
server {
ip="202.54.6.5";
timeout=260;
interval=900;
uptest=none;
ping_timeout=500;
purge_cache=off;
caching=on;
}
server {
ip="202.54.1.30";
timeout=260;
interval=900;
uptest=none;
ping_timeout=500;
purge_cache=off;
caching=on;
}
server {
ip="202.9.128.6";
timeout=260;
interval=900;
uptest=none;
ping_timeout=500;
purge_cache=off;
caching=on;
}
source {
ttl=86400;
owner="localhost.";
serve_aliases=on;
file="/etc/hosts";
}
/*
rr {
ttl=86400;
owner="localhost.";
name="localhost.";
a="127.0.0.1";
soa="localhost.","root.localhost.",42,86400,900,86400,86400;
}
rr {
ttl=86400;
owner="localhost.";
name="1.0.0.127.in-addr.arpa.";
ptr="localhost.";
soa="localhost.","root.localhost.",42,86400,900,86400,86400;
} */</pre>
<HR NOSHADE>
<p>This is a sample working configuration (DNS servers are of VSNL
an Indian ISP).You must edit servers section of pdnsd.conf to suit
your needs.(Fill in DNS servers of your ISP aginst IP entry). Start
PDNSD once more and connect to the Internet. Type nslookup and do a query
for say, yahoo.com. The server will respond somthing like:
<pre>&gt; yahoo.com
Server: debian
Address: 127.0.0.1
Non-authoritative answer:
Name: yahoo.com
Addresses: 204.71.200.245</pre>
Stop PDNSD and disconnect from the Internet. Start PDNSD again and query
for yahoo.com through nslookup. If you are geting the same answer as above
, fine have a coffee and relax. Else if, there is something wrong and ....??
<h2>
5. Tweaking configuration files.</h2>
If you are using BIND as your primary nameserver, one can very well make
PDNSD the secondary one. But here you have Catch-22 situation, on which
local IP and port would you make PDNSD listen ? Look at ragOO's pdnsd.conf
file and named.conf file:
<p>[pdnsd.conf]
<pre>global {
perm_cache=2048;
cache_dir="/var/cache/pdnsd";
max_ttl=604800;
run_as="nobody";
paranoid=off;
server_port=53
server_ip="127.0.0.2";
}</pre>
[named.conf--relevant section only]
<pre>options {
directory "/var/cache/bind";
forward first;
forwarders {127.0.0.2;202.54.6.1;202.54.1.30};
};</pre>
ragOO's GNU/Linux machine has local (lo) IP addresses from 127.0.0.1 to
8.This is the same in all GNU/Linux systems and one has the option to specify
127.0.0.2 to be the alternate local server. PDNSD listens on Port 53 and
note that 127.0.0.2 is the first forwarder in named.conf. This means that
your machine/BIND looks up the PDNSD cached records for a number match
of the address you/the client program has requested, if not there then
it queries the DNS resolvers of your ISP; in order it goes.
<br>
<br>
<h2>
6. FAQs.</h2>
The follwing question and answer is from the correspondence I had with
Thoams Meostl author of pdnsd.
<p>Q. I had some problem with your default installation. The cache was
not growing. It was stuck at 4 bytes. I changed permissions to 'nobody'
and it started growing. Probably a problem with my configuration. Will
you please let me know the correct file permissions for /var/cache/pdnsd
and /var/cache/pdnsd/pdnsd.cache ?
<p>A. The best thing is to give the user who runs pdnsd write permissions
to the cache directory (and of course to the cache file): chown &lt;user&gt;
/var/cache/pdnsd chmod 0700 /var/cache/pdnsd chown &lt;user&gt; /var/cache/pdnsd.cache
chmod 0600 /var/cache/pdnsd/pdnsd.cache
<p>Where the permissions can of course be more liberal, if you want. The
ones given are the minimum required permissions. The default permissions
"make install" sets on the files are also OK. The only important thing
is to chown the file. Normally, "make install" should also chown the cache
file (maybe a bug? If it didn't for you, please drop me a mail).
<h2>
7. Credits.</h2>
Thanks to the author of this nifty utility, Thomas Moestl for clarifying
certain points and doubts. He made me a better user of PDNSD :-) !
<p>Thanks to <a href="mailto:vmathew@eth.net"> Manoj Victor Mathew</a>
and <a href="mailto:ragu@vsnl.com"> Raghavendra Bhat</a> (ragOO)
for mentioning about 'pdnsd' during one of the ILUG-Cochin meets. ragOO
edited and modified the draft heavily and encouraged me to keep on modifying
the draft.
<p>Last but not the least, to all users of this elegant program who may
have found this rant useful. Enjoy....;
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Copyright &copy; 2001, Sunil Thomas Thonikuzhiyil.<BR>
Copying license <A HREF="../copying.html">http://www.linuxgazette.com/copying.html</A><BR>
Published in Issue 65 of <i>Linux Gazette</i>, April 2001</H5>
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