[U-Boot-Users] How to use tftp to book kernel image and mount remote root fs

[Steven Woody]

On Wed, May 14, 2008 at 10:05 AM, Jerry Van Baren <gvb.uboot at gmail.com> wrote:
> Steven Woody wrote:
>>
>> On Tue, May 13, 2008 at 2:07 PM, Wolfgang Denk <wd at denx.de> wrote:
>>>
>>> Dear Steven,
>>>
>>> in message <ed4892840805121852t46d4c4d0rd52a9eb129121f7b at mail.gmail.com>
>>> you wrote:
>>>>
>>>> Q1:
>>>>
>>>> Both 5.9.5.1 (
>>
>> http://www.denx.de/wiki/view/DULG/UBootCmdGroupDownload#Section_5.9.5.1.
>>>>
>>>> ) and 5.9.5.6 (
>>>> http://www.denx.de/wiki/view/DULG/UBootCmdGroupDownload#Section_5.9.5.6.
>>>> ) talk about booting image via network, but there are only few lines
>>>> of description about these commands.  I don't know which one I should
>>>> use, tftpboot or bootp? And, for each one, what's the requirement on
>>>
>>> That depends on what you want to do. Do you understand the differecne
>>> between TFTP and BOOTP (resp. DHCP) protocols?
>>
>> I understand tftp and bootp as a function of current DHCP, but I don't
>> know how tftp and bootp is related.  Would you suggest me something to
>> read? Thank you.
>
> Bootp is a boot protocol that allows a system to query a server to figure
> out what IP it is assigned and what executable file to load (typically via
> TFTP).  DHCP is the successor to bootp.
>
> TFTP is a file transfer protocol that allows a system to load its executable
> (typically) file from the server.
>
> <http://www.linuxjournal.com/article/5465> (ignore RARP, it is deprecated).
>
> HTH,
> gvb
>

Thank you Jerry, I now understand TFTP and BOOTP should on a same
host, the 'filename' parameter in dhcpd.conf specified the boot image
file which can be download via tftp by u-boot. And, nfs server can be
on another server, the 'next-server' parameter in dhcpd.conf specified
the ip address of the nfs server.

But one thing I am not clear:  the u-boot's bootargs variable uses
  nfsroot=${serverip}:${rootpath}
are the 'serverip' and 'rootpath' set by querying BOOT server in
u-boot's bootp stage? if so, serverip should equals to the next-server
parameter in dhcpd.conf, and rootpath should equal to root-path
parameter in dhcpd.conf.  You see, in u-boot, it is rootpath, but in
dhcpd.conf, it is root-path,  is there a typo in the u-boot manual?

And, in the u-boot manual, I see, the `filename' parameter in
dhcpd.conf is something like /tftproot/uImage, but I think it should
be /uImage, because the /tftproot should be the root path of tftp
server, to the client, the path name should be /uImage, am I right?

Thank you very much.



 $rootpath, was this variable set by querying BOOTP server?

-- 
woody

then sun rose thinly from the sea and the old man could see the other
boats, low on the water and well in toward the shore, spread out
across the current.