Changing dhcp variables served to pxe booting clients

[M&CS sysadmin team - RFG]

Thanks! That seems to work nicely.

Many thanks!

Richard

Glenn Satchell wrote:
> Hi Richard,
>
> Here's what I use. The PXE.mtftp-ip was needed with a newer bios that
> expected them. Seems harmless to leave them in for older bios systems.
>
> # Option definitions for PXE
> option space PXE code width 1 length width 1 hash size 3;
> option PXE.mtftp-ip code 1 = ip-address;
> # PXE boots for jumpstarting x86 boxes
> class "PXE" {
>   match if substring(option vendor-class-identifier, 0, 9) = "PXEClient";
>   next-server drill.uniq.com.au;
>   filename "pxegrub.I86PC.Solaris_10-1";
>   # 10 minutes should be long enough for PXE
>   max-lease-time 600;
>   # don't use multicast tftp option
>   vendor-option-space PXE;
>   option PXE.mtftp-ip 0.0.0.0;
> }
> subnet 192.168.14.0 netmask 255.255.255.0 {
>   option routers grinder.uniq.com.au;
>   option subnet-mask 255.255.255.0;
>   option broadcast-address 192.168.14.255;
>   pool {
>     range 192.168.14.230 192.168.14.253;
>   }
> }
>
> Any other PXE specific things can be put in the PXE class.
>
> HTH.
>
> regards,
> -glenn
> --
> Glenn Satchell     mailto:glenn.satchell at uniq.com.au | I telephoned the
> Uniq Advances Pty Ltd         http://www.uniq.com.au | swine flu info
> PO Box 70 Paddington NSW Australia 2021              | line and all I got
> tel:0409-458-580  tel:02-9380-6360  fax:02-9380-6416 | was crackling.
>
>
>
>   
>> Date: Tue, 14 Jul 2009 15:12:34 +0100
>> From: Richard Grant <rfg3 at mcs.le.ac.uk>
>> To: dhcp-users at lists.isc.org
>> Subject: Changing dhcp variables served to pxe booting clients
>>
>> Hi,
>>
>> I'm trying to do something which seems like it should be easy, but I cannot
>> figure out how to make it work...
>>
>> The situation is that we have a bunch of PCs that dual boot. When they are
>> running normally they need to be given a certain set of dhcp 
>> information. When
>> they are PXE booting to reinstall linux, they need to be given a 
>> different set
>> of dhcp information (a different router, next-server, etc).
>>
>> Previously, with a different version of DHCP, we could set up a macro which
>> contained the different sets of DHCP information. Then when we wanted to
>> reinstall a PC we just changed which macro it used.
>>
>> It looks like we should be able to use if...else statements in DHCP to do
>> something similar. I tried:
>>
>> subnet xxx.xxx.xxx.0 netmask 255.255.255.0 {
>>   if option user-class = "install" {
>>      <reinstalling dhcp parameters>
>>   } else {
>>      <normal dhcp parameters>
>>   }
>> }
>>
>> with host entries outside the subnet of the form:
>>
>> host pc1000 { hardware ethernet 00:11:22:33:44:55; fixed-address pc1000; 
>> option user-class install;}
>>
>> However, this never returned true, and always just returned the 'else'
>> parameters, even though the user-class option which set to "install".
>>
>> I have tried all sorts of other methods, but couldn't get anything to work.
>>
>> Can anyone help me find a way to make the above system work? The object 
>> is to
>> have a script which changes the value of the user-class parameter to 
>> "install"
>> when we want to perform a reinstall, and to "noinstall" or something 
>> else when
>> we want the PC to boot as normal.
>>
>> Alternately, is there a way to get it so that the dhcp server can 
>> automatically
>> tell if the PC is PXE booting, and hence serve it different parameters? 
>> I saw
>> an example that seemed to do this, but it didn't actually work. It was 
>> of the
>> form:
>>
>> if substring(option vendor-class-identifier, 0, 9) = "PXEClient" {
>>      <reinstalling dhcp parameters>
>> } else {
>>      <normal dhcp parameters>
>> }
>>
>> Any idea how this might be made to work? Does that 
>> vendor-class-identifier only
>> with certain hardware, something like that?
>>
>> If there is any more information I need to give about my setup, then 
>> just let
>> me know. I'm pretty new to this sort of functionality in DHCP.
>>
>> Thanks,
>>
>> Richard Grant
>> _______________________________________________
>> dhcp-users mailing list
>> dhcp-users at lists.isc.org
>> https://lists.isc.org/mailman/listinfo/dhcp-users
>>     
>
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