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Re: Hosts file



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
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