Hosts file

[John Summerfield]

Aaron Konstam wrote:
> On Sat, 2007-10-13 at 16:34 +0930, Tim wrote:
>> On Sat, 2007-10-13 at 08:29 +0800, Ed Greshko wrote:
>>> But, having things done automatically when you are unaware they are
>>> going to be done is never helpful, IMHO.
>> Yes, and no...  If it works, and the user wouldn't have been able to
>> figure things out, it would have been helpful to them.  Which tends to
>> be the point of things like DHCP, network manager, and so on...
>>
>>> In this case, if indeed the hosts file is being overwritten by DHCP,
>>> it is certainly not what the OP anticipated or wanted since he is left
>>> with a blank hosts file. 
>> Though, I'd say that's a fault condition.
>>
>> The sorts of things that a DHCP client can and can't do are user
>> configurable, by customising "/etc/dhclient.conf"
>>
> You have it sort of backwards. /etc/dhclient.conf tells the DHCP server
> what the client wants it do do. It does not determine what the DHCP
> server is allowed to do on its own volition. If the file is empty and it
> is on my client the hosts file should,d be untouched.
> 
> Quickly looking at the man page for that file I see no provision for the
> host file to be changed but maybe it is too early in the morning. 

dhcp clients can be configured to ask for particular information, and 
dhcp servers can be configured to provide particular information.

If all goes well, the dhcp server will provide all the information the 
client asks for, but the client is under no obligation to use all the 
information the server provides.

Documentation commonly available on how to configure ISC DHCPD3 to 
support PXE booting for (eg) network installs generally omits to mention 
  how to provide that information only to a PXE BIOS. Mostly clients 
ignore next-server and filename and any other information they don't want.

How some of that information might get into /etc/hosts depends on the 
scripts supporting the DHCP client. Use rpm to list the files in your 
dhcp client package, and peruse anything in /etc or any [s]bin 
directory, and the documentation for hints.

How it's done depends on the actual dhcp client (common ones in Linux 
are dhcpd and dhclient, and I'm a bit confused about who provides which 
and in which releases). I've configured a laptop (originally running FC3 
but upgraded to FC5 or so) to use the provided DNS servers to 
reconfigure bind and restart it, but the particulars of that technique 
don't work with SUSE's equivalent package.

It would be interesting to see OP's /etc/hosts file before and after 
it's updated: that may provide some clue as to what's happening. I'm 
guessing it gets an entry like this:

192.168.9.131 numbat.demo.lan numbat
which wouldn't do me any harm, but wouldn't help anyone else find numbat.

There might be a comment that provides a clue.




-- 

Cheers
John

-- spambait
1aaaaaaa at coco.merseine.nu  Z1aaaaaaa at coco.merseine.nu

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