Erwan Velu wrote:
> Hey folks,
> I saw the lastest qemu support pxe so I tried it using the following 
> command:
>
> qemu -hda /tmp/a.img -net nic n- user -boot n
>
> Note that now qemu support pxe mode, the mandatory -hda option is no 
> more mandatory but this is not directly linked to my patch.
> I saw qemu integrates a dhcp & a tftp server but they don't seems to 
> be configured/developped for a pxe boot process.
> Qemu says "no filename" and exits.

Hi Erwan,

I really like the idea of your patch.  Of course, the hard coding is not 
really reasonable :-)  Also, PXE is an x86-ism.  What you've really done 
is added a mechanism to publish a BOOTP name.  We do need to add a new 
option too as one may want to use -boot n without publishing a BOOTP 
filename.

Using your patch as a basis, I've written three patches.  The first one 
is the tsize negotiation fix for the TFTP server.  The second adds a 
-bootp option for specifying the location of the BOOTP image.  The third 
changes the -tftp option to take root directory.  The end result, is 
that now you can say:

qemu -hda /tmp/a.img -boot n -tftp ~/tftpboot -bootp /pxelinux.0

And you get the same results without the hard coding.  What do you think?

Regards,

Anthony Liguori

> A friend of I asked me "how do you boot using pxe in qemu when you 
> don't have a dhcp & a tftp server ?".
> So I started to look how we can do that, I modified bootp to catch the 
> field 60 of a dhcp request to find if its a pxe request or not.
> If yes, I set the filename to "/pxelinux.0", currently this is 
> harcoded, maybe you can help me to find a better way to specify a 
> bootloader.
>
> Then, I've patched the tftp server to change the default rootdir in my 
> home dir. "~/tftpboot". This is just for a Proof-of-concept, other 
> methods could be fine. We can also imagine searching in a path 
> restricted to the admin and then in the user dir. So it can give the 
> admin the ability of defining some pxe boot for all the vm of a 
> system  or in the user dir if the user wants to have a special pxe 
> boot scheme.
>
> The last patch I did on the tftp server, is to allow the tsize 
> negociation because pxelinux needs it.
>
> This patch apply to 0.9.0, once it is applied and compiled here come 
> the test procedure:
>
> create a ~/tftpboot/pxelinux.cfg directory
> copy pxelinux.0 in ~/tfptboot/
> create a pxelinux configuration file called "default" in 
> ~/tftpboot/pxelinux.cfg
>
> Et voila ;)
>
> Just call "qemu -hda /tmp/a.img -net nic n- user -boot n", it will 
> start pxelinux.
>
> I think this patch is very usefull because it give users & admin the 
> ability to use pxe inside the VM without installing the full 
> configuration (dhcp,tftp).
> This patch is mainly a proof-of-concept, this patch can be improved, 
> comments and feedback are welcome.
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