[lug] Hostname, Knoppix, where does it come from?

Nate Duehr nate at natetech.com
Thu Jun 29 03:12:19 MDT 2006

On Jun 28, 2006, at 8:42 PM, Bob Collins wrote:

> Ed Moxley wrote:
>> On Wed, 2006-06-28 at 17:06, Bob Collins wrote:
>>> I decided to install a fresh version of SuSE 10.0. Everything  
>>> went fine except that this is what I get when I ping from another  
>>> computer on my local network. bob at matt:~> ping linux.local PING  
>>> linux.local ( 56(84) bytes of data. 64 bytes from  
>>> Knoppix ( icmp_seq=1 ttl=64 time=0.139 ms 64 bytes  
>>> from Knoppix ( icmp_seq=5 ttl=64 time=0.167 ms
>> Do you really want the box to be called linux.local? You might try  
>> changing back to dhcp from the static config and changing the host  
>> name to a single name like linuxwhatever (without the dot) and see  
>> if the Knoppix name goes away.
> Linux is not a good name for a computer box, but it has had that  
> name for many years. All of the computers on my local area network  
> have the the box_name.domain_name where domain_name is local. I add  
> the .local to linux in the email because of the other meanings for  
> linux, which makes it confusing.
> Tech support at peakpeak.com answered my email by saying I should  
> contact Novell/SuSE tech support. I copied another person there who  
> seems to know a little more about linux and what is going on, but I  
> really don't expect much help from peakpeak.com.
> I should have checked them out a little better, but I am sure they  
> are not as bad as msm.com, the Qwest default internet provider.
> Thank you all for your help.
> Bob


Here's my 3AM comments.  Hope they're not too rambling and make at  
least a little sense to you after posting at this horrible hour.   
(Can't sleep.)

 From many years of experience with DNS -- and making some  
assumptions about how your 2wire brand router works, I'd say the  
following happened:

First off, your router is apparently acting as your local DNS server  
for anything on your internal LAN subnet, and it hands out it's own  
IP address for serving DNS requests in the initial DHCP request from  
your clients.  (This is pretty easy to check - if all your DHCP  
clients show your router's internal IP address as their DNS server,  
that's what it's doing.)  MANY small router/firewalls do this  
nowadays to make setup easy for everyone - no more setting up a DNS  
server in the router - it just proxy's the requests.

You booted Knoppix and its DHCP client has the relatively (many  
years, but...) new feature turned on that not only asks the router  
for an internal private IP address, but also sends a DNS update  
packet using it's machine name to the router.

Your router now believes that's the name of the machine on that  
particular internal IP address.  It also appears that your router  
"splits" your DNS and keeps track of machine names internally using  
the 2wire.com domain name internally also.  (You don't own or operate  
the 2wire.com domain and theoretically should have no possible way to  
update/add/change it.  So assuming 2wire isn't doing some kind of  
free dynamic DNS service for all of their routers -- which I very  
highly doubt -- this naming phenomenon is limted to your local LAN  
behind the 2wire router.  No one "on the Internet" can see or use any  
of the DNS names you've mentioned from the outside world of the  
Internet itself.)

Okay having worked on a couple of 2wire routers before I can say two  
things about them.  They're set up by default to make it virtually  
impossible for a user to screw up their Internet connectivity -- they  
make all the "choices" you should be making for yourself about your  
network for you.  Second, they usually have an "Advanced" mode where  
you can override certain behaviors, but it wouldn't surprise me at  
all if they didn't provide a way to turn this auto-DNS junk off  

So, a couple of thoughts...

Did you try rebooting the 2wire router?  If you're lucky and they  
don't store DHCP information in non-volatile memory (flash), perhaps  
it'll simply "forget" it ever knew a name for that IP address after a  

Next, you could always turn on the same feature that Knoppix is using  
to update DNS from your other Linux.  If Knoppix can set/change the  
name in the router during its DHCP sessions, so can your other  
Linux.  How easy or difficult that might be is probably something  
you'd need to research, but I'd start with Googling for "Dynamic DNS  
+ DHCP + <Distro name>" and going from there.  It's probably  
relatively easy to tell your SuSE to do it, but I've never done it on  
SuSE, so I can't elaborate at all.

Finally -- the simplest question... why do you care what the 2wire  
router calls the machine on your internal LAN?  If the early  
assumption is correct that 2wire doesn't "publish" this name in any  
way out to the Net, it simply doesn't matter.  You can put a hosts  
file entry on the other machines to give that machine ten different  
names that work that you can call it by, other than the one you don't  
like... or you could even set up an internal DNS server if there is  
some way to tell the 2wire NOT to hand out its own IP address as a  
DNS server for your internal LAN.  I doubt they give you this option,  
the 2wire routers are pretty limited, trying to make things "easier"  
on you.  All they accomplish is making it SO easy, you don't really  
know what's going on and missed a number of key things like learning  
how hostnames and DNS resolve, which is pretty basic core networking  

To summarize: Don't worry about it.  Use the real IP address or add a  
hosts file entry or two to call it what you want on your internal  
network.  If you REALLY want to know how to straighten it out, you're  
going to have to do the research to figure out how Knoppix set it in  
the first place and duplicate the effort on SuSE.  Linux is Linux, so  
it *can* be done, but it may be easy (if the feature is built-in to  
SuSE and just not enabled) or difficult (have to find and build the  
DHCP client Knoppix is using if your SuSE's version won't do it).

The only other serious comment I might offer is this:  If you want to  
learn how something like networking, routing and DHCP work, including  
the DNS server assignment, etc... the absolute best way would be to  
find everything labeled "Auto" in the 2wire and set it to manual --  
and attempt to build your network from the ground up, and get it  
working, with all static IP's, hostnames, perhaps a DNS server... if  
you feel like purchasing a domain name, etc... everything set up and  
configured by YOU, not the engineer that built the 2wire router --  
they built it to do everything for you but butter your morning  
toast... and it sounds like it's doing just that... anytime a  
computer isn't doing what you want it to, do like you just did and  
dive in with both feet and figure out why -- it's only doing what it  
was programmed or told to do by *someone*... in this case, it  
certainly sounds like that would be the 2wire engineers.

It also sounds like peakpeak.com has NOTHING to do with what you're  
seeing -- other than choose a really cheesy hard-to-configure- 
manually router for their customers.  But I guarantee they did it to  
keep setups simple and installation easy and to save themselves  
having to directly support users needing assistance with network setup.

Oh yeah, the reason your ping is even showing a name on the replies  
is that your client doing the ping is doing a reverse DNS lookup on  
the internal address of your linux machine.  The 2wire is just  
handing it the name it knows about.  Changing the machine's internal  
address could/should allow you to work from an IP that 2wire knows no  
information about.

Nate Duehr
nate at natetech.com

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