LINUX NEWS
Resources & Links From www.CramSession.com
July 18, 2002TABLE OF CONTENTS
1) Sean’s Notes
2) Linux News
Going for the RHCE?
Linux@Walmart.com
Symantec to Acquire SecurityFocus3) Linux Resources
Which is Better, ext3 or ReiserFS
What's in /etc/sysconfig?
Crazy Perl Tricks
NetSaint vs Big Brother4) App o’ the Week
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1) Sean’s Notes
You don’t have to register a domain in order to play with DNS. Having a DNS server for your local LAN can be helpful, both in a corporate setting, and at home. Today, we’re going to set up DNS with our own top level domain (TLD).
.com is an example of a TLD. When you look up www.cramsession.com, your resolver hits the root servers looking for “cramsession”. It gets a referral to Cramsession’s nameservers, who know all about the cramsession domain (often called a zone). They then return the answer to “www.cramsession.com”.
We can create our own TLD, perhaps called “linux”. Unfortunately, the world won’t know about it, but in a private network, everyone can make use of it. Thus, you can have “www.linux”, or “payroll.linux”, all in the privacy of your own network.
Most distributions have BIND, so I’ll let you install it from a package rather than going through the install with you. Two reasons - there are few options so it’s rather boring. The second reason is that if you use package management, you can rely on your distribution to provide updates (you do check regularly, right?)
/etc/named.conf controls most of what BIND does. The first thing we have to do is define a new zone for our “linux” TLD:
zone “linux” IN { type master; file “db.linux”; };
Be careful with the semi-colons. named.conf is very picky about syntax.
What we’ve done here is created an Internet zone (that’s the IN) called “linux”. “type master” means that it’s going to be the one with the actual zone files. The file directive tells BIND where to look for the zone file. Unless you fully qualify the file, it’s relative to /var/named.
The next thing is to define /var/named/db.linux:
\@ IN SOA @ postmaster.linux. ( 200207181 ; serial YYYYMMDD# 3H ; refresh 15M ; retry 1W ; expiry 1D ) ; minimum
Every zone must have an SOA record, which stands for “Start Of Authority”. The important stuff there is the line marked ‘serial’. It identifies the zone at a particular point in time. Whenever you make a change, update the serial. Remove nameservers cache this information, and the serial lets them know the latest revision. I prefer to embed the date in the serial, and appending a single digit in case I make multiple updates in a day. It just helps when debugging, so I know the last time it was modified. The other numbers are various timeouts.
The “postmaster.linux” is supposed to be the email address of the administrator, with the @ replaced by a .. Feel free to put a throwaway one in there, it harks back to the days when you could trust people out on the Internet. The @’s in the SOA record are expanded to “linux.” by the name server. Rather than typing it in for every zone you create, you can use this as a standard header.
The next records that go into your zone file identify your nameservers. In an internal environment, it’s likely that they’re already known anyway, but it’s good practice:
IN NS linux.(192.168.1.1 is the address of my internal name server, substitute as appropriate)
Like directories, the name server files have a concept of relative paths. We are currently in the “linux.” zone. The trailing dot means “STOP!”. If you leave off the trailing dot, the name server appends the zone if you leave it off. So, if you ever see something like:
linux name server linux.linux.
–it’s a clue that you forgot that dot.
On the left side, I’ve got
<blank> IN NS linux.
That blank gets “linux.” tacked on to the end of it. Similarly, we could have done–
linux. IN NS linux.
However, relying on the nameserver to add in the extra stuff saves you a lot of typing later.
At this point, you could fire up named, and you’d have a fully functioning nameserver for the linux tld for your own private use. Not very useful without the other records, though.
’A’ records define hosts. If 192.168.1.2 were a web server, I could point www.linux to it:
www IN A 192.168.1.2
Update your serial, and restart the name services. (You might notice there is no . at the end of the IP address. ‘A’ records expect an IP address on the right hand side, and will not implicitly append the domain)
host www.linux
www.linux has address 192.168.1.2
Just to be correct, we defined linux. as our name server, but we haven’t defined an A record for it:
linux. IN A 192.168.1.1
–which gives us a hostname of “linux”.
http://support.algx.net/cst/dns/dns2.html
–has a great tutorial on the various types of records you can place within your zone.
Creating your own TLD is an easy way to learn DNS without having to register your own domain. It’s also a great thing for companies, a url like http://payroll.mycorp is quite distinguishable as an internal URL, and easier to remember.
The techniques we used here today are also the exact same that are used when you want to register a domain on the Internet. Just substitute our “linux” for your “whatever.tld” and you’re off to the races!
Long live the Penguin,
Sean swalberg@cramsession.com
2) Linux News
Going for the RHCE?
Here’s a poll on the Red Hat Linux Certified Engineer board. Are you planning on taking the RHCE exam? Why or why not?
http://boards.cramsession.com/boards/vbm.asp?mY7924
Linux@Walmart.com
Here’s some more information, including a link to the online store, for the Walmart Linux PCs.
http://www.theregus.com/content/4/25601.html
Symantec to Acquire SecurityFocus
Not sure how I feel about this one… Security Focus has long been a great source of security information, including the famous BugTraq list, and a great jobs list. I hope that being bought out by a vendor doesn’t compromise their objectivity.
http://www.symantec.com/press/2002/n020717.html
3) Linux Resources
Which is Better, ext3 or ReiserFS?
ext3 and ReiserFS are two popular journalled filesystems for Linux. Each has their own distinct advantages, and both make claims to be the fastest. Here’s some objective performance tests. Note, though, the author used some settings on both filesystems that you’d only want to use if your hard drive controller is battery backed – not always realistic, and defeats part of the purpose of having a journalled filesystem.
http://www.gurulabs.com/ext3-reiserfs.html
What’s in /etc/sysconfig?
One of my favourite features of Red Hat is that most everything can be configured out of /etc/sysconfig, making automation with scripts that much easier. Though I find looking at the init scripts the best way to find out what variables to set, this web page has a good listing of what files and variables are available.
http://www.redhat.com/support/resources/howto/sysconfig.html
Crazy Perl Tricks
This perl article illustrates an interesting concept – serving web pages out of a tarball. I’m trying to think of a practical use for it, but it’s educational to say the least.
http://www.linux-mag.com/2002-04/perl_01.html
NetSaint vs Big Brother
Both NetSaint and Big Brother are programs to monitor services and boxes on your network, and to alert you if there are problems. This document is a very good comparison of both programs.
http://userpages.umbc.edu/~smelam1/nsbb.pdf
4) App o’ the Week
It’s an Open Source version of Civilization. It’s got network play, and looks pretty good! They just released 1.13.0, a major milestone for the project.
http://www.freeciv.org
(C) 2002 BrainBuzz.com, Inc. All Rights Reserved.
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