LINUX NEWS
RESOURCES & LINKS FROM BRAINBUZZ.COM
Thursday, September 20, 2001
Read By Over 7,000 Linux Enthusiasts Weekly!TABLE OF CONTENTS
1) Sean’s Notes
2) Linux News
Hacking Linux Exposed
Linux+ Exam Details
Write a Game, Win the Loot
IPStor package lifts storage to new capacities3) Linux Resources
But Who Will Support it?
And is it Supported?
Separated by a Common Operating System
Mandrake Demos and Tutorials
Heat Emergency4) App o’ the week
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1) Sean's Notes
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Going through my list of common questions, I found a good one:
"I can ping a host by IP, but not by name".
Many would immediately jump to the conclusion that something
must be wrong with the DNS settings, and they'd probably be
right. But, where do you set up the DNS server in Linux?
Before I jump into all the configuration files, some things
have to be said about naming. Like Windows, DNS isn't the
only way to name a computer. NIS, the Network Information
Service, can be used to store the mappings, as can NIS+
(an advanced version made by SUN), text files, and
many others. As with Windows, there is a pecking order
of sorts: one database is consulted before another, and
the searching stops once a match is found.
Unlike Windows, though, it's pretty trivial to change
all of this by editing one file. The C library implements
a call named "gethostbyname", which is used universally
in UNIX to find out the address of a machine given its
name. Note that "address" can be pretty much anything --
we're not limiting ourselves to IP addresses. One of the
things that gethostbyname() does is to consult a line in
/etc/nsswitch.conf to find out where it should start looking.
nsswitch.conf keeps a line for each of several databases,
including the password file, keys, protocols, and yes,
hostnames. On my system, I see a line with
hosts: files nisplus dns
This is processed in order. First, my system will look in a
particular file. For names, it's /etc/hosts. No match? Check
out NIS+. I'm not using NIS+, so it will go to DNS. If it can
find a match in DNS, then great, return that. Otherwise, the
host isn't found. By playing with the order, you can change
the precedence of the lookups, or even remove a map entirely
(i.e., you can set up your computer to only use NIS+ for, say,
name resolution).
Once the library has decided to use DNS, it has to
know what server to use. To find this out, it consults
/etc/resolv.conf. This file can further alter the behaviour
several ways.
Nameservers are listed with the "nameserver" keyword:
nameserver 1.2.3.4
nameserver 5.6.7.8
will allow the use of two nameservers for DNS resolution.
By default, they are tried in the order listed, so 5.6.7.8
will only get consulted if 1.2.3.4 times out.
The "options rotate" command will allow you to round-robin
between your listed nameserver.
Those who have configured DNS on Windows machines will
likely remember the "domain name" and "search order"
options. If my domain is "example.com", it would be
desirable to try to find hosts within that domain if they
fail elsewhere. Thus, a query to the name "test" will first
be tried as "test", and then "test.example.com". Set your
default domain name with
domain example.com
If you would like additional domains added to this list,
use the "search" keyword. (note that "domain" is a special
form of "search")
search example.org
Thus, if "test" isn't found in example.com, it will be tried
in example.org. Be careful using this, though, as it will
start to generate a lot of DNS traffic as the searchlist grows.
So, in quick summary, /etc/nsswitch.conf tells the system
where to look for various things. If it is to look in files,
/etc/hosts is where the names are kept. If it has to go to
DNS, /etc/resolv.conf is consulted for more info.
Solaris users should be especially wary of nsswitch.conf,
as by default, DNS isn't in there (at least before Solaris 7).
Either add it in, or look at the other nsswitch.\* files for
a template to copy over.
DNS is only part of the way that the system resolves names.
Understanding the whole process of resolution can help you
troubleshoot.
Long live the Penguin,
Sean
swalberg@brainbuzz.com
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2) Linux News
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Hacking Linux Exposed
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This time around, I review "Hacking Linux Exposed", a comprehensive
book on Linux and network security. If you're in the market
for a book on security, give this one serious consideration.
http://itresources.brainbuzz.com/tutorials/tutorial.asp?t=S1TU1442
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Linux+ Exam Details
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Many of you are familiar with the A+ exam from CompTia, along
with all the other certs they offer such as Server+, Network+,
and more. Did you know they offer Linux+? The beta period closed
some time ago, and the exam is almost ready to go live. Brainbuzz
user bcabalic dug up all the details on the format and costs in
case you were wondering.
http://boards.brainbuzz.com/boards/vbm.asp?m64351
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Write a Game, Win the Loot
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No Starch press, Loki Software, and Linux Journal bring you a
contest to go with the release of their "Programming Linux Games"
book (review coming soon!). The best SDL based game that fits
under a Meg gets some really neat prizes, not to mention the bragging
rights. There are other restrictions to encourage people to join, so
give it a look!
http://www.nostarch.com/?games
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IPStor package lifts storage to new capacities
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If you thought SANs (Storage Area Networks) were limited to big
systems, think again. This Linux based product acts as a SAN,
providing geographically disperse, redundant disk storage. The
cool thing is the way that it uses drivers on the clients to
map the IP address to a local SCSI device... No expensive fibre
channel cards!
http://www.zdnet.com/products/stories/reviews/0,4161,2806610,00.htm
l
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3) Linux Resources
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But Who Will Support it?
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One of the harder things to pitch to the suits is the support
aspect of Linux. There are many companies that will support
your developers, desktop, and servers. ZDNet was kind enough
to perform a detailed review of 12 different vendors, and
even give us all the data.
http://techupdate.zdnet.com/techupdate/stories/main/0%2c14179%2c280
8791-1%2c
00.html
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And is it Supported?
---------------------
Making sure hardware is supported by Linux can be a daunting
task. The Hardware HOWTO is a comprehensive list of
hardware that is supported under the standard kernel, or by
third parties. It's also good in that it tells you if the
driver is distributed in binary or source format. Binary is
fine, but imposes difficulties when trying to change your
kernel version.
http://www.ibiblio.org/pub/linux/docs/howto/Hardware-HOWTO
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Separated by a Common Operating System
---------------------------------------
This article starts off by following the author's trial of Debian
and SuSE, and ends up finding out that they're completely different.
Not only are they different from each other, but also he finds that
most distributions have major differences and incompatibilities.
Is this a sort of accidental fragmentation? At this point, the only
common thing through distributions is the kernel itself, but is this
necessarily a bad thing?
http://www.linuxplanet.com/linuxplanet/opinions/3543/1/
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Mandrake Demos and Tutorials
-----------------------------
Not being a Mandrake user myself, I was impressed at the depth
of this part of their site. They have demos of some of their
software, basic tutorials for newbies, and other highlights.
If you're interested in seeing what Mandrake has to offer,
but don't have the time to try an install, this is certainly
be a good place to start.
http://www.linux-mandrake.com/en/demos/
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Heat Emergency
---------------
As you might have deduced from the increasing size of heatsinks
and fans, CPUs these days generate a lot of heat. What would
happen if the CPU overheated? Someone decided to put this to
the test by removing the fan and heatsink entirely. The results
were surprising, to say the least.
http://www.tomshardware.com/cpu/01q3/010917/index.html
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4) App o' the week
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With the advent of Microsoft Windows 2000 brings easier access
to thin clients through the use of Microsoft's RDP protocol.
Access a Win2K desktop from DOS, any version of windows, and
now, Linux. Nope, it's not supported by Microsoft, but finally
you can connect to a Terminal Server to get at those corporate
apps from your Linux box.
http://www.rdesktop.org
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