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<H4>
"Linux Gazette...<I>making Linux just a little more fun!</I>"
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<center>
<H1><font color="maroon">Linux Installation Primer, Part Seven Version 1999.02.14</font></H1>
<H4>By <a href="mailto:rjenkins@qni.com">Ron Jenkins</a></H4>
</center>
<P> <HR> <P>
<P><FONT SIZE=-1><B>Copyright </B><FONT FACE="Symbol">&Oacute;</FONT><FONT FACE="Courier New">
1998, 1999 by Ron Jenkins. This work is provided on an "as is" basis. The
author provides no warranty whatsoever, either express or implied, regarding
the work, including warranties with respect to its merchantability or fitness
for any particular purpose.</FONT></FONT>
<P><FONT FACE="Courier New"><FONT SIZE=-1>The author welcomes corrections
and suggestions. He can be reached by electronic mail at <A HREF="mailto:rjenkins@qni.com">rjenkins@qni.com</A>,
or at his personal homepage: <A HREF="http://www.qni.com/~rjenkins/">http://www.qni.com/~rjenkins/</A>.</FONT></FONT>
<P><FONT FACE="Courier New"><FONT SIZE=-1>Corrections, as well as updated
versions of all of the author's works may be found at the URL listed above.</FONT></FONT>
<P><FONT FACE="Courier New"><FONT SIZE=-1>NOTE: As you can see, I am moving
to a new ISP. Please bear with me as I get everything in working order.
The e-mail address is functional; the web site is semi operational, I will
add to it as I get the time.</FONT></FONT>
<P><FONT FACE="Courier New"><FONT SIZE=-1>SPECIAL NOTE: Due to the quantity
of correspondence I receive, if you are submitting a question or request
for problem resolution, please see my homepage listed above for suggestions
on information to provide.</FONT></FONT>
<P><B><FONT FACE="Courier New"><FONT SIZE=-1>Operating Systems Covered/Supported:</FONT></FONT></B>
<BR><B><FONT FACE="Courier New"><FONT SIZE=-1>Slackware version 3.6</FONT></FONT></B>
<BR><B><FONT FACE="Courier New"><FONT SIZE=-1>RedHat version 5.1</FONT></FONT></B>
<BR><B><FONT FACE="Courier New"><FONT SIZE=-1>Windows NT Server version
4.0</FONT></FONT></B>
<BR><B><FONT FACE="Courier New"><FONT SIZE=-1>Windows NT Workstation version
4.0</FONT></FONT></B>
<P><B><I><FONT FACE="Courier New"><FONT SIZE=-1>I only test my columns
on the operating systems specified. I don?t have access to a MAC, I don?t
use Windows 95, and have no plans to use Windows 98. If someone would care
to provide equivalent instructions for any of the above operating systems,
I will be happy to include them in my documents.</FONT></FONT></I></B>
<P><B><FONT FACE="Courier New"><FONT SIZE=-1>Part Seven: Internet Gateway
performance tuning and tips</FONT></FONT></B>
<BR><FONT FACE="Courier New"><FONT SIZE=-1>In a continuation of last month's
column, we will look at some ideas, tips and tricks to improve the performance
of our Internet Gateway, as well as some advanced configuration options.</FONT></FONT>
<P><FONT FACE="Courier New"><FONT SIZE=-1>As with each installment of this
series, there will be some operations required by each distribution that
may or may not be different in another. I will diverge from the generalized
information when necessary, as always.</FONT></FONT>
<P><FONT FACE="Courier New"><FONT SIZE=-1>In this installment, I will cover
the following topics:</FONT></FONT>
<UL>
<LI>
<FONT FACE="Courier New"><FONT SIZE=-1>Overview of Performance tuning and
enhancement.</FONT></FONT></LI>
<LI>
<FONT FACE="Courier New"><FONT SIZE=-1>Techniques for performance enhancement.</FONT></FONT></LI>
<LI>
<FONT FACE="Courier New"><FONT SIZE=-1>WAN connection upgrades.</FONT></FONT></LI>
<LI>
<FONT FACE="Courier New"><FONT SIZE=-1>Hardware upgrades.</FONT></FONT></LI>
<LI>
<FONT FACE="Courier New"><FONT SIZE=-1>Software upgrades.</FONT></FONT></LI>
<LI>
<FONT FACE="Courier New"><FONT SIZE=-1>Caching options.</FONT></FONT></LI>
<LI>
<FONT FACE="Courier New"><FONT SIZE=-1>General tips and tricks.</FONT></FONT></LI>
<LI>
<FONT FACE="Courier New"><FONT SIZE=-1>References.</FONT></FONT></LI>
<LI>
<FONT FACE="Courier New"><FONT SIZE=-1>Resources for further information.</FONT></FONT></LI>
<LI>
<FONT FACE="Courier New"><FONT SIZE=-1>About the Author.</FONT></FONT></LI>
</UL>
<B><FONT FACE="Courier New"><FONT SIZE=-1>Assumptions applicable to this
column:</FONT></FONT></B>
<BR><B><FONT FACE="Courier New"><FONT SIZE=-1>It is assumed you have read
my previous installments in this series, if not, I suggest you review them
first if you find any of the terms or concepts here confusing.</FONT></FONT></B>
<P><B><FONT FACE="Courier New"><FONT SIZE=-1>Also, throughout the article,
I shall use the term WAN connection and PPP connection interchangeably.</FONT></FONT></B>
<P><B><FONT FACE="Courier New"><FONT SIZE=-1>Overview of Performance tuning
and enhancement:</FONT></FONT></B>
<BR><FONT FACE="Courier New"><FONT SIZE=-1>Performance enhancement, like
any other project, requires an analysis of the cost of the enhancement
versus the amount of improvement.</FONT></FONT>
<P><FONT FACE="Courier New"><FONT SIZE=-1>What we will endeavor to accomplish
here is to improve the performance of our gateway, using a variety of techniques,
while keeping the additional cost as low as possible.</FONT></FONT>
<P><FONT FACE="Courier New"><FONT SIZE=-1>For any method suggested here,
there will be a trade off. Some of the following suggestions may or may
not be applicable to your own unique situation.</FONT></FONT>
<P><FONT FACE="Courier New"><FONT SIZE=-1>Some of these techniques will
provide a real, measurable, and noticeable improvement, while others will
only become apparent through long term analysis, or examination of various
statistical reporting methods available to you. The ability to accurately
measure the performance of your gateway machine is essential to effective
tuning.</FONT></FONT>
<P><FONT FACE="Courier New"><FONT SIZE=-1>As we go along and become familiar
with each technique, I will also introduce appropriate methods of measuring
these techniques, and therefore accurately measure the amount or percentage
of improvement.</FONT></FONT>
<P><B><FONT FACE="Courier New"><FONT SIZE=-1>Techniques for performance
enhancement:</FONT></FONT></B>
<BR><FONT FACE="Courier New"><FONT SIZE=-1>Although some of the ideas and
techniques discussed here will be applicable to other types of machines,
such as file servers and workstations, the primary focus of this column
will be geared toward the specific enhancement of gateway machines.</FONT></FONT>
<P><FONT FACE="Courier New"><FONT SIZE=-1>In the context of this assumption,
the following techniques, in descending order of importance will provide
the most improvement in the operation and speed of the gateway machine:</FONT></FONT>
<OL>
<LI>
<FONT FACE="Courier New"><FONT SIZE=-1>WAN connection upgrades.</FONT></FONT></LI>
<LI>
<FONT FACE="Courier New"><FONT SIZE=-1>Hardware upgrades.</FONT></FONT></LI>
<LI>
<FONT FACE="Courier New"><FONT SIZE=-1>Software upgrades.</FONT></FONT></LI>
<LI>
<FONT FACE="Courier New"><FONT SIZE=-1>Caching options.</FONT></FONT></LI>
</OL>
<FONT FACE="Courier New"><FONT SIZE=-1>Finally, I will discuss some general
tips and tricks for measuring the performance of your gateway, as well
as some ideas for areas of improvement.</FONT></FONT>
<P><B><FONT FACE="Courier New"><FONT SIZE=-1>WAN connection upgrades:</FONT></FONT></B>
<BR><FONT FACE="Courier New"><FONT SIZE=-1>The single most effective method
for increasing the performance of your Internet Gateway is to upgrade the
speed of your connection to the Internet.</FONT></FONT>
<P><FONT FACE="Courier New"><FONT SIZE=-1>This can take the form of a dedicated
or dialup connection in most cases. Some of the options you may want to
consider include:</FONT></FONT>
<UL>
<LI>
<FONT FACE="Courier New"><FONT SIZE=-1>Many ISP's offer "dual modem" service.
This is a technique whereby the two individual modem connections are "bound"
together using multi-link PPP. The performance enhancement is slightly
less than the sum of the two individual connections.</FONT></FONT></LI>
<LI>
<FONT FACE="Courier New"><FONT SIZE=-1>56K modems, provided they are not
software modems, more commonly known as "WinModems," may be an option.
I have been told by one of my readers that the external models work well,
and if the internal model is NOT a soft modem as described above, it should
work as well. (Thanks go to Gerald McGlew for setting me straight on this
information.)</FONT></FONT></LI>
<LI>
<FONT FACE="Courier New"><FONT SIZE=-1>Presently, an Integrated Services
Digital Network (ISDN) line, commonly known as a Basic Rate Interface,
or BRI, is one of the best ways to remarkably improve the performance of
your Gateway machine. In my area, an ISDN line, with unlimited usage, costs
about $80.00 per month. The cost for a dial up ISDN connection in my area
is about $50.00 total cost (line charge + ISP access) ~$130.00.</FONT></FONT></LI>
<LI>
<FONT FACE="Courier New"><FONT SIZE=-1>Another possibility would be a cable
modem, although I know very little about these devices, as they are not
available in my area, so I do not know how cost effective they are.</FONT></FONT></LI>
<LI>
<FONT FACE="Courier New"><FONT SIZE=-1>In some areas of the country, Digital
Satellite Network systems are available. These work well, as long as you
have a clear path to the satellite. However, the satellite connection is
only unidirectional, meaning that it only moves FROM the remote station
TO your PC. This is called the downlink. A separate method of access is
required for the uplink, or your requests TO the remote network. This can
be anything from a simple modem to a dedicated connection.</FONT></FONT></LI>
</UL>
<FONT FACE="Courier New"><FONT SIZE=-1>Measuring the performance of your
WAN connection -</FONT></FONT>
<BR><FONT FACE="Courier New"><FONT SIZE=-1>There are several programs and
utilities that can help you here, one that I use quite a bit is a program
called netwatch, which is handy for general monitoring of your network
and the speed of your router (your Internet gateway.) This utility is not
provided as part of the normal distribution of RedHat, but is included
with Slackware 3.6. There is an RPM of an older version available at any
of the RedHat mirror sites, in the /powertools/ directory.</FONT></FONT>
<P><FONT FACE="Courier New"><FONT SIZE=-1>For checking the real time condition
of your WAN connection, as well as the effectiveness of any compression
options you may be using, pppstats is very helpful. This utility should
be available on both Slackware and RedHat machines.</FONT></FONT>
<P><B><FONT FACE="Courier New"><FONT SIZE=-1>Hardware upgrades:</FONT></FONT></B>
<BR><FONT FACE="Courier New"><FONT SIZE=-1>To improve the performance of
your local network access, RAM and disk subsystems are king. Provided your
motherboard has sufficient cache to handle it, put as much RAM as you can
afford in your server and gateway machines.</FONT></FONT>
<P><FONT FACE="Courier New"><FONT SIZE=-1>Another crucial area is the disk
subsystem. Although there have been significant advances in ATA technology,
such as EIDE, UDMA, and so on, the standard for heavy, continuous use and
high performance is still the Small Computer Systems Interface, or SCSI
device.</FONT></FONT>
<P><FONT FACE="Courier New"><FONT SIZE=-1>It is important to note that
IDE drives are SEQUENTIAL access devices, meaning each request for information
must "stand in line" and wait for it's turn. SCSI drives are CONCURRENT
access devices, meaning multiple requests can be serviced simultaneously.</FONT></FONT>
<P><FONT FACE="Courier New"><FONT SIZE=-1>While the price differential
between IDE devices and comparable SCSI devices was prohibitive in the
past, at the preset time, the difference is negligible. Consider Ultra
(20MBS) drives a minimum, Ultra Wide (40MBS) drives better.</FONT></FONT>
<P><FONT FACE="Courier New"><FONT SIZE=-1>A SCSI subsystem is comprised
of four basic parts</FONT></FONT>
<UL>
<LI>
<FONT FACE="Courier New"><FONT SIZE=-1>the host adapter, or card that is
inserted in your PC and coordinates all communication between the SCSI
devices and your computer.</FONT></FONT></LI>
<LI>
<FONT FACE="Courier New"><FONT SIZE=-1>The SCSI bus, upon which all the
data interchange takes place. Usually a 40 or 50 pin cable, depending on
the speed of the host.</FONT></FONT></LI>
<LI>
<FONT FACE="Courier New"><FONT SIZE=-1>The SCSI devices, which may include
disks, scanners, tape drives, and many other devices. The number of devices
allowed on a given bus depends on the speed of the host as well, but is
not limited to four devices, like a comparable IDE bus.</FONT></FONT></LI>
<LI>
<FONT FACE="Courier New"><FONT SIZE=-1>The termination devices. Like the
bus network we discussed in December, a SCSI bus requires termination at
both ends, just like a 10BASE2 coaxial network. The termination can be
active or passive, and may or may not require an additional device to be
attached, especially on external SCSI devices.</FONT></FONT></LI>
</UL>
<FONT FACE="Courier New"><FONT SIZE=-1>You may notice I do not mention
U2W devices here. The support for these devices, as far as I know, is still
in the development stage, so I would wait awhile on these devices. Besides,
they are waaaaay expensive!</FONT></FONT>
<P><B><FONT FACE="Courier New"><FONT SIZE=-1>NOTE: Unless you are planning
on implementing some of the caching techniques described below, a disk
subsystem upgrade will not provide a noticeable performance enhancement.</FONT></FONT></B>
<P><B><FONT FACE="Courier New"><FONT SIZE=-1>Simple routing and masquerading
are done in the kernel, on the fly, causing minimal interaction with the
disk.</FONT></FONT></B>
<P><B><FONT FACE="Courier New"><FONT SIZE=-1>However, if the machine also
doubles as a file server, web server, or something other than just an Internet
Gateway, then it is worth considering.</FONT></FONT></B>
<P><B><FONT FACE="Courier New"><FONT SIZE=-1>Software upgrades:</FONT></FONT></B>
<BR><FONT FACE="Courier New"><FONT SIZE=-1>In the area of software enhancements,
here are some options to consider:</FONT></FONT>
<P><FONT FACE="Courier New"><FONT SIZE=-1>PPP Software - You may want to
consider upgrading your PPP software if your distribution does not contain
PPP version 2.3.0 or greater.&nbsp; This version contains support for the
demand dialing option, thus eliminating the need for diald or any such
extra stuff.</FONT></FONT>
<P><FONT FACE="Courier New"><FONT SIZE=-1>It also supports a more robust
scripting method based on ppp-xx scripts, usually prepared at installation
time and requiring only some editing to make them functional. These files
are usually located in /etc/ppp and/or /usr/sbin.</FONT></FONT>
<P><FONT FACE="Courier New"><FONT SIZE=-1>Data Compression - A comprehensive
explanation of Data compression theory is beyond the scope of this article,
so briefly, here is an overview of compression methods and how they can
improve the apparent speed with which traffic flows through your WAN interface.</FONT></FONT>
<P><FONT FACE="Courier New"><FONT SIZE=-1>Van Jacobson (VJ) Compression
- This is enabled by default in most Linux distributions of the PPP daemon.</FONT></FONT>
<P><FONT FACE="Courier New"><FONT SIZE=-1>BSD Compression (bsdcomp) - Another
compression scheme, usually disabled by default. You will be required to
load a module, or re-compile the kernel to include support for this.</FONT></FONT>
<P><FONT FACE="Courier New"><FONT SIZE=-1>Deflate Compression - Yet another
compression scheme, also disabled by default.</FONT></FONT>
<P><FONT FACE="Courier New"><FONT SIZE=-1>Any one of, and/or combination
of these compression schemes may or may not improve the apparent performance
of your PPP connection. To enable, disable, or adjust the parameters for
any or all of these compression schemes, see the pppd man pages. Experiment
with them, using netwatch to measure any speed changes, and pppstats to
measure the amount of compression.</FONT></FONT>
<P><FONT FACE="Courier New"><FONT SIZE=-1>BIND - The Berkley Internet Name
Daemon (BIND), commonly called named, is the service responsible for hostname
to IP address translation on the Internet, most often referred to as Domain
Name Service, or DNS<B>**</B>.</FONT></FONT>
<P><FONT FACE="Courier New"><FONT SIZE=-1>While it is impractical to run
your own full blown DNS server (unless of course you have your own domain,
and a block of assigned IP's,) It can be helpful to run what is known as
a "caching only" nameserver.</FONT></FONT>
<P><FONT FACE="Courier New"><FONT SIZE=-1>Whenever you request an object
on the Internet, whether it be a web page, ftp site, news server, or whatever,
you usually issue the request in the form of a hostname/path_to_object/
format. When your request goes out, it is handed off to the DNS server
specified in your resolv.conf file first.</FONT></FONT>
<P><FONT FACE="Courier New"><FONT SIZE=-1>Since the DNS system is hierarchical,
like an upside down pyramid, with the point on the bottom being the DNS
machine in your resolv.conf file, your DNS machine only knows about machines
local to it's own network<B>*</B>, in this case, your ISP's. This information
is contained in what are known as "zone" files, which are simply ASCII
text files that list information about a "zone" or domain in a standardized
format.</FONT></FONT>
<P><FONT FACE="Courier New"><FONT SIZE=-1>If the request cannot be resolved
by this machine, it then consults the next higher machine in the pyramid,
as so on until ultimately, if necessary, the query reaches the "root.servers"
responsible for all the *.com, *.edu, *.net domains and so on.</FONT></FONT>
<P><FONT FACE="Courier New"><FONT SIZE=-1>Finally, at some point, after
much communication back and forth across the WAN connection, the hostname
you requested will be converted into an IP address, and sent back to your
computer.</FONT></FONT>
<P><FONT FACE="Courier New"><FONT SIZE=-1>Clearly, there's a significant
amount of communication going on in the background to let us meat based
computing devices do the "dub dub dub" deal.</FONT></FONT>
<P><FONT FACE="Courier New"><FONT SIZE=-1>What a caching nameserver does
simply put, is to "remember" these name to IP resolutions for a period
of time, so the next time a particular object is requested, the nameserver
can service the request locally, without having to go outside the local
network. This is way cool for two reasons. It makes name resolution appear
much faster, and reduces traffic on the WAN.</FONT></FONT>
<P><FONT FACE="Courier New"><FONT SIZE=-1>The downside to this is that
each initial, or "new" request will take slightly longer to return to your
computer. As I said before, everything is a trade off. Usually, the latency
is nominal. This technique is almost always a good idea.</FONT></FONT>
<DIR>
<DIR><B><I><FONT FACE="Courier New"><FONT SIZE=-1>* Well sort of. It is
possible for your ISP to be aware of other networks beyond the ones contained
in the root.servers file, but this is irrelevant in the scenario we are
discussing here.</FONT></FONT></I></B>
<P><B><I><FONT FACE="Courier New"><FONT SIZE=-1>** Actually, BIND is comprised
of a number of programs, each performing a specific function. The most
important piece of the puzzle is the resolver.</FONT></FONT></I></B></DIR>
</DIR>
<FONT FACE="Courier New"><FONT SIZE=-1>Apache - The Apache http server
contains provisions for enabling some caching options, thus reducing WAN
traffic. Check the Apache documentation for more information.</FONT></FONT>
<P><FONT FACE="Courier New"><FONT SIZE=-1>Squid - This is a web proxy/caching
software suite that is infinitely configurable, and supports many services.
To find out more about Squid, and whether it is right for your particular
installation, see the resources section at the end of this document.</FONT></FONT>
<P><FONT FACE="Courier New"><FONT SIZE=-1>Leafnode - This is a replacement
for the Network News Transport Protocol (NNTP) server usually used in most
UNIX installations. It is small, easy to configure, and takes up a fraction
of the disk space of the normal Internet News (INN) software. The trade
off is that it does not scale well, and can really tie up your WAN connection
when it initially downloads the articles available from the newsgroups
you have selected (See the cron section of the General Tips and Tricks
for some ways to minimize this congestion.) To find out more about Leafnode,
and whether it is right for your particular installation, see the resources
section at the end of this document.</FONT></FONT>
<P><B><FONT FACE="Courier New"><FONT SIZE=-1>Caching options:</FONT></FONT></B>
<UL>
<LI>
<FONT FACE="Courier New"><FONT SIZE=-1>Advantages of cache options - Whenever
you are able to store a document (such as a web page or news article,)
or a data object (such as a name to IP resolution,) locally, this allows
your gateway to service your request locally, thus reducing the amount
of traffic across your WAN (PPP) connection. This is a good thing, because
the apparent speed with which your request is serviced is greatly increased,
while the WAN connection is left available for other requests and tasks.
Additionally, if you have the disk space for it, spooling your own news
is a great idea as well. This allows local network access to your Usenet
spool, and keeps the download (usually called a fetch or suck because it
sucks up all your bandwidth,) on the local net, and off the WAN.</FONT></FONT></LI>
<LI>
<FONT FACE="Courier New"><FONT SIZE=-1>Disadvantages of cache options -
However, there is a tradeoff involved here. This type of caching works
best for documents and data that are considered "static" or infrequently
changed. Depending on the expiry parameter set for your caching service
(the amount of time a document or object resides locally on your machine
before it is considered "stale" and deleted,) you may find yourself looking
at "yesterday's news." This is primarily a concern in the web caching area,
less so in the news although your articles will not be refreshed in "real
time", and negligible in the nameserver.</FONT></FONT></LI>
<LI>
<FONT FACE="Courier New"><FONT SIZE=-1>Configuration of a caching only
name server - BIND may or may not be installed on your machine already,
depending on your choices at installation time. If your distribution does
not contain BIND version 8.1.x or greater, I strongly recommend you upgrade.
The 4.x.x version are no longer in development, and the added features
included in the 8.x.x version, such as dynamic zone transfers, and simplified
configuration, make it worth the upgrade. See the resources section for
the URL of the Internet Software Consortium (ISC) which develops and maintains
BIND.</FONT></FONT></LI>
</UL>
<FONT FACE="Courier New"><FONT SIZE=-1>Slackware 3.6 - The Slackware distribution
will require you to do a little work to enable the nameserver. This is
really a good thing, because when you set it up yourself, you will be better
equipped with more of an understanding of how the process works, and therefore,
how to diagnose and correct problems when they develop.</FONT></FONT>
<P><FONT FACE="Courier New"><FONT SIZE=-1>First, you will need a directory
called /var/named. If it is not already there, create it.</FONT></FONT>
<P><FONT FACE="Courier New"><FONT SIZE=-1>Next, you will need a file containing
listings of all the root servers, and a file that serves as your local
information, or "zone" file. These files should be named root.cache, and
127.0.0, respectively. Examples of these two files may be found in the
DNS-HOWTO, or the Cricket book listed in the resources section.</FONT></FONT>
<P><FONT FACE="Courier New"><FONT SIZE=-1>Finally, you will need a named.conf
file, which passes the start up options to BIND. For a caching nameserver,
it should look something like the following:</FONT></FONT>
<P><FONT FACE="Courier New"><FONT SIZE=-1>// Config file for caching only
name server</FONT></FONT>
<BR><FONT FACE="Courier New"><FONT SIZE=-1>options {</FONT></FONT>
<BR><FONT FACE="Courier New"><FONT SIZE=-1>directory "var/named";</FONT></FONT>
<BR><FONT FACE="Courier New"><FONT SIZE=-1>//Uncomment the line below if
you are behind a</FONT></FONT>
<BR><FONT FACE="Courier New"><FONT SIZE=-1>//firewall, and you can?t get
things to work:</FONT></FONT>
<BR><FONT FACE="Courier New"><FONT SIZE=-1>// query-source port 53;</FONT></FONT>
<BR><FONT FACE="Courier New"><FONT SIZE=-1>};</FONT></FONT>
<BR><FONT FACE="Courier New"><FONT SIZE=-1>zone "." {</FONT></FONT>
<BR><FONT FACE="Courier New"><FONT SIZE=-1>type hint;</FONT></FONT>
<BR><FONT FACE="Courier New"><FONT SIZE=-1>file "root.cache";</FONT></FONT>
<BR><FONT FACE="Courier New"><FONT SIZE=-1>};</FONT></FONT>
<BR><FONT FACE="Courier New"><FONT SIZE=-1>zone "0.0.127.in-addr.arpa"
{</FONT></FONT>
<BR><FONT FACE="Courier New"><FONT SIZE=-1>type master;</FONT></FONT>
<BR><FONT FACE="Courier New"><FONT SIZE=-1>file "127.0.0";</FONT></FONT>
<BR><FONT FACE="Courier New"><FONT SIZE=-1>};</FONT></FONT>
<BR><FONT FACE="Courier New"><FONT SIZE=-1>// End Config file example</FONT></FONT>
<P><FONT FACE="Courier New"><FONT SIZE=-1>Those of you who are familiar
with the C/C++ programming language will notice the similarity of the syntax
of the named.conf file.</FONT></FONT>
<P><FONT FACE="Courier New"><FONT SIZE=-1>Briefly, the first section delineates
the working directory, the second section tells the resolver where to look
for the root servers file, and the last section is your "zone" file. This
file should live in the /etc directory.</FONT></FONT>
<P><FONT FACE="Courier New"><FONT SIZE=-1>Finally, edit your resolv.conf
file on the gateway machine to point first to itself, then to your ISP
for name resolution:</FONT></FONT>
<P><FONT FACE="Courier New"><FONT SIZE=-1>search <A HREF="http://home.net/">home.net</A></FONT></FONT>
<BR><FONT FACE="Courier New"><FONT SIZE=-1>nameserver 127.0.0.1</FONT></FONT>
<BR><FONT FACE="Courier New"><FONT SIZE=-1>nameserver &lt;your ISP primary
DNS></FONT></FONT>
<BR><FONT FACE="Courier New"><FONT SIZE=-1>nameserver &lt;your ISP secondary
DNS></FONT></FONT>
<P><FONT FACE="Courier New"><FONT SIZE=-1>Then finish up by pointing all
your <A HREF="http://home.net/">home.net</A> clients to the gateway for
resolution:</FONT></FONT>
<P><FONT FACE="Courier New"><FONT SIZE=-1>search <A HREF="http://home.net/">home.net</A></FONT></FONT>
<BR><FONT FACE="Courier New"><FONT SIZE=-1>nameserver 192.168.1.1</FONT></FONT>
<P><FONT FACE="Courier New"><FONT SIZE=-1>RedHat 5.x - when you install
the RPM, it automagically should install as a caching server. If not, then
see above for the required files and proper named.conf examples.</FONT></FONT>
<P><B><FONT FACE="Courier New"><FONT SIZE=-1>General tips and tricks:</FONT></FONT></B>
<UL>
<LI>
<FONT FACE="Courier New"><FONT SIZE=-1>Late night cron tricks - Cron (short
for chronometer,) is a more user friendly (supposedly ;-)) front end to
the at daemon. This daemon allows the unattended execution of scripts and
commands on precise days at specific times. This is very handy for automating
many of the drudge tasks inherent on a UNIX box, such as log rotation,
ftp jobs, or in our case, news and caching server functions. This information
is contained in files called crontab files. There may or may not be more
than one of these files present on your system, depending on how it was
set up at installation, and how many users you may have. This file or files
live in the /var/spool/cron/crontabs directory.</FONT></FONT></LI>
<LI>
<FONT FACE="Courier New"><FONT SIZE=-1>Automating function's with cron
- To edit, or add an entry in the crontab file, use the command - crontab
-e &lt;return>. Once the file is open, entries are made in the format &lt;minutes>
&lt;hours> &lt;days> &lt;weeks> &lt;months> commands. Null entries are
represented by an asterix (*). For an example, you will probably want to
schedule your leafnode newsfeeds, as well as any extensive cache downloads
in the early hours of the morning when you have the least amount of users
on the system. To start the newsfeed (fetch) every morning at 4:00 a.m.,
the entry would be:</FONT></FONT></LI>
</UL>
<FONT FACE="Courier New"><FONT SIZE=-1>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
0 4 * * * /usr/sbin/fetch</FONT></FONT>
<UL>
<LI>
<FONT FACE="Courier New"><FONT SIZE=-1>Calling scripts from cron - There
will be times when you want to execute a series of commands, or pass many
options to one or more commands, and entering them over and over at the
command line becomes a bummer. Enter shell programming. This is nothing
more than a file that contains a series of commands to be executed, then
exited after the last command is done. This is handy for any number of
things. Indeed, the unicom file from last month is a shell script. As an
example, say you wanted to remove your wtmp file, and create a new one
every hour. The script for this might look something like:</FONT></FONT></LI>
</UL>
<FONT FACE="Courier New"><FONT SIZE=-1>#!/bin/sh #all scripts should start
with your preferred shell</FONT></FONT>
<BR><FONT FACE="Courier New"><FONT SIZE=-1>rm -f /var/log/wtmp #this removes
the old file</FONT></FONT>
<BR><FONT FACE="Courier New"><FONT SIZE=-1>touch /var/log/wtmp #this creates
the new file</FONT></FONT>
<BR><FONT FACE="Courier New"><FONT SIZE=-1>echo "wtmp cleaned" > /var/log/wtmp.log
#this just lets me know the script ran</FONT></FONT>
<P><FONT FACE="Courier New"><FONT SIZE=-1>Shell scripts can be created
using any of the many text editors available on your Linux system. Let?s
say we named this file wtmpclean. To make it executable by the system,
simply issue the chmod command:</FONT></FONT>
<P><FONT FACE="Courier New"><FONT SIZE=-1>chmod +x wtmpclean</FONT></FONT>
<P><FONT FACE="Courier New"><FONT SIZE=-1>To call this script from cron,
and have it run every hour, your crontab entry would be something like:</FONT></FONT>
<P><FONT FACE="Courier New"><FONT SIZE=-1>0 * * * * /usr/sbin/wtmpclean</FONT></FONT>
<UL>
<LI>
<FONT FACE="Courier New"><FONT SIZE=-1>Browser cache settings - Netscape
has a feature that allows you to adjust the size and behavior of your browser?s
disk and memory cache. These are areas set aside on your disk and in RAM
to "keep" your most recently requested browser objects, like an html page,
a .gif or .jpg file, etc. To adjust these settings, from the Netscape menu
bar choose Edit/Preferences/Advanced/Cache, Subject to RAM and disk space
limitations, you can increase/decrease the size of your Disk and Memory
cache, and choose how frequently your browser will go out across the WAN
to compare the document in the cache to the document at it?s original location.
Keep in mind the limitations mentioned previously. This is probably best
set to "Once per session" unless you are trading stocks or something that
requires frequent updates.</FONT></FONT></LI>
<LI>
<FONT FACE="Courier New"><FONT SIZE=-1>Tweaking your modem - Most modems
have extra features available that may or may not improve the performance
and behavior of your modem. Check the manufacturer?s documentation and
experiment.</FONT></FONT></LI>
<LI>
<FONT FACE="Courier New"><FONT SIZE=-1>Data line conditioning - For a small
additional monthly charge, you can have the phone company "condition" your
line, or optimize it for data versus voice communications. This may or
may not be useful to you, it is usually most helpful if you are in a rural
area, or some other area that experiences excessive static or degradation
of line quality.</FONT></FONT></LI>
</UL>
<B><FONT FACE="Courier New"><FONT SIZE=-1>References:</FONT></FONT></B>
<BR><FONT FACE="Courier New"><FONT SIZE=-1>Previous Columns:</FONT></FONT>
<BR><FONT FACE="Courier New"><FONT SIZE=-1>Parts 4,5, and 6.</FONT></FONT>
<P><FONT FACE="Courier New"><FONT SIZE=-1>Other:</FONT></FONT>
<BR><FONT FACE="Courier New"><FONT SIZE=-1>Pppd man pages</FONT></FONT>
<BR><FONT FACE="Courier New"><FONT SIZE=-1>Cron man pages</FONT></FONT>
<BR><FONT FACE="Courier New"><FONT SIZE=-1>Leafnode man pages</FONT></FONT>
<BR><FONT FACE="Courier New"><FONT SIZE=-1>PPP HOW-TO</FONT></FONT>
<BR><FONT FACE="Courier New"><FONT SIZE=-1>SERIAL HOW-TO</FONT></FONT>
<BR><FONT FACE="Courier New"><FONT SIZE=-1>DNS-HOWTO</FONT></FONT>
<P><B><FONT FACE="Courier New"><FONT SIZE=-1>Resources for further information:</FONT></FONT></B>
<BR><FONT FACE="Courier New"><FONT SIZE=-1>Web Resources:</FONT></FONT>
<BR><FONT FACE="Courier New"><FONT SIZE=-1><A HREF="http://www.redhat.com/">http://www.redhat.com/</A></FONT></FONT>
<BR><FONT FACE="Courier New"><FONT SIZE=-1><A HREF="http://www.slackware.com/">http://www.slackware.com/</A></FONT></FONT>
<BR><FONT FACE="Courier New"><FONT SIZE=-1><A HREF="http://metalab.unc.edu/LDP/">http://metalab.unc.edu/LDP/</A></FONT></FONT>
<BR><FONT FACE="Courier New"><FONT SIZE=-1><A HREF="http://www.linuxresources.com/">http://www.linuxresources.com/</A></FONT></FONT>
<BR><FONT FACE="Courier New"><FONT SIZE=-1><A HREF="http://metalab.unc.edu/">http://metalab.unc.edu/</A></FONT></FONT>
<BR><FONT FACE="Courier New"><FONT SIZE=-1><A HREF="http://www.isc.org/">http://www.isc.org/</A></FONT></FONT>
<BR><FONT FACE="Courier New"><FONT SIZE=-1><A HREF="http://www.apache.org/">http://www.apache.org/</A></FONT></FONT>
<BR><FONT FACE="Courier New"><FONT SIZE=-1>Squid Software:</FONT></FONT>
<BR><FONT FACE="Courier New"><FONT SIZE=-1><A HREF="http://squid.nlanr.net/">http://squid.nlanr.net</A></FONT></FONT>
<BR><FONT FACE="Courier New"><FONT SIZE=-1>Leafnode Software:</FONT></FONT>
<BR><FONT FACE="Courier New"><FONT SIZE=-1><A HREF="http://wpxx02.toxi.uni-wuerzburg.de/~krasel/leafnode.html">http://wpxx02.toxi.uni-wuerzburg.de/~krasel/leafnode.html</A></FONT></FONT>
<BR><FONT FACE="Courier New"><FONT SIZE=-1>Netwatch software:</FONT></FONT>
<BR><FONT FACE="Courier New"><FONT SIZE=-1><A HREF="ftp://ftp.slctech.org/pub/">ftp://ftp.slctech.org/pub/</A></FONT></FONT>
<P><FONT FACE="Courier New"><FONT SIZE=-1>Newsgroups:</FONT></FONT>
<BR><FONT FACE="Courier New"><FONT SIZE=-1>alt.unix.wizards</FONT></FONT>
<BR><FONT FACE="Courier New"><FONT SIZE=-1>comp.security.unix</FONT></FONT>
<BR><FONT FACE="Courier New"><FONT SIZE=-1>comp.unix.admin</FONT></FONT>
<BR><FONT FACE="Courier New"><FONT SIZE=-1>alt.os.linux.slackware</FONT></FONT>
<BR><FONT FACE="Courier New"><FONT SIZE=-1>comp.os.linux.networking</FONT></FONT>
<BR><FONT FACE="Courier New"><FONT SIZE=-1>comp.os.linux.hardware</FONT></FONT>
<BR><FONT FACE="Courier New"><FONT SIZE=-1>linux.redhat.misc</FONT></FONT>
<P><FONT FACE="Courier New"><FONT SIZE=-1>Print Materials:</FONT></FONT>
<BR><FONT FACE="Courier New"><FONT SIZE=-1>DNS and BIND (The Cricket Book)
- 2<SUP>nd</SUP> edition (O?Reilly &amp; Associates)</FONT></FONT>
<P><B><FONT FACE="Courier New"><FONT SIZE=-1>As always, I?ve ran way long
this month. Look for the Advanced Services information next month.</FONT></FONT></B>
<P> <HR> <P>
<center><H4>Previous ``Linux Installation Primer'' Columns</H4></center>
<p>
<A HREF="../issue32/jenkins1.html">Linux Installation Primer #1, September
1998</A><BR>
<A HREF="../issue33/jenkins2.html">Linux Installation Primer #2, October
1998</A><BR>
<A HREF="../issue34/jenkins3.html">Linux Installation Primer #3, November
1998</A><BR>
<A HREF="../issue35/jenkins4.html">Linux Installation Primer #4, December
1998</A><BR>
<A HREF="../issue36/jenkins5.html">Linux Installation Primer #5, January
1999</A><BR>
<A HREF="../issue37/jenkins6.html">Linux Installation Primer #6, February
1999</A><BR>
<!--===================================================================-->
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<center><H5>Copyright &copy; 1999, Ron Jenkins <BR>
Published in Issue 38 of <i>Linux Gazette</i>, March 1999</H5></center>
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