[gPXE] How to modify the code can not get DHCP information on the2nd

[Shao Miller]

sqwbwh wrote:
> At 2010-11-05 22:39:05，"ShaoMiller"<Shao.Miller at yrdsb.edu.on.ca> wrote:
>
>>>>>     sqwbwh wrote:
>>>>>>
>>>>>>
>>>>>>     How to modify the code can not get DHCP information on the
>>>>>>     2nd?(GPXE only used to boot the system from ISCSI)
>>>>>>     Is to remove this step.
>>>>>>     net0: 00:0 c:: 29:08:11:35 on UNDI-PCI02: 01.0 (OPEN)
>>>>>>     [Link: up, TX: 0 TXE: 0 TX: 0 rxe: 0]
>>>>>>     DHCP (net0 00:0 c: 29:08:11: d5 ).... ok
>>>>>>     net0: 192.168.0.202/255.255.255.0
>>>>>>
>>>>>>
>>>>>>     This can speed up boot speed.
>>>>>>     Normal GPXE run to start from the boot system tftp process
>>>>>>     takes about 8 seconds or so
>>>>>>     If removed from the second time for DHCP information will
>>>>>>     only need a very quick 2.5 seconds.
>>>>>>
>>>>     Miller, Shao wrote:
>>>>>     You most likely want the 'use-cached' option.  It is DHCP gPXE encapsulated option number 178.  Or, you can set it in an embedded script:
>>>>>
>>>>>       #!gpxe
>>>>>       set use-cached 1
>>>>>       autoboot
>>>>     Gene Cumm wrote:
>>>>>
>>>>>     What file and version are you using? It sounds as if you're using
>>>>>     undionly.kpxe or a .pxe file. undionly.kkpxe will skip this second
>>>>>     DHCP request but certain hardware/firmware has issues with this,
>>>>>     assuming you trust the stability of your OEM's PXE/UNDI stack.
>>>>>
>>>     sqwbwh wrote:
>>>>     Shao Miller
>>>>
>>>>     The method is successful.
>>>>     Thank you
>>>     sqwbwh wrote:
>>>>     yes
>>>>     thankyou Shao Miller
>>>>     Your method is useful ：）
>>     Miller, Shao wrote:
>>>     You’re quite welcome, and thanks for including the list on your
>>>     other reply. :) Have a nice day. - Shao
>>
>     sqwbwh wrote:
>>     Shao Miller
>>     1:
>>     i use :
>>     " set it in an embedded script:
>>>
>>>     #!gpxe
>>>     set use-cached 1
>>>     autoboot
>>     it's good
>>     2:
>>     "It is DHCP gPXE encapsulated option number 178"
>>     Specifically to ask how to use this method?
>>     What can explain it in detail?
>>     thank~you
>     I enjoy using the search feature at the gPXE (Etherboot) wiki.
>     Please see:
>
>     http://etherboot.org/wiki/doku.php?do=search&id=encapsulated&fulltext=Search
>     http://etherboot.org/wiki/msdhcp
>     http://etherboot.org/wiki/dhcpd
>
> ShaoMiller
> Use the search function.
> Use hyperlinks to provide you with three options for the introduction
> of 178 not found.
> 178 keyword search does not find use-cached search did not find the
> relevant presentation.
>
> Hehe. Could you give me the answer it?. English is almost a maze for me
>

I'm afraid that I'm not sure how to explain gPXE encapsulated options
any better than they are explained in the wiki. DHCP option 175 should
be a string of bytes. Within that byte sequence, there are sub-options.
'use-cached' is sub-option 178. So your DHCP option 175 could look like:

0xB2 0x01 0x01

where,

0xB2 : DHCP gPXE encapsulated option 178.
0x01 : The encapsulated option's value occupies 1 byte.
0x01 : The encapsulated option's value is 1 (true).

I do not know which DHCP service you use, so I do not know how you can
reconfigure your service to give PXE clients this 'use-cached' option
via DHCP.

- Shao Miller
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