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[PATCH] Xen Grub-style boot loader
Ok, here's something I hacked up this afternoon to try and get the ball
moving on this.

It's a simple grub style ncurses application. This is my ncurses app so
it's probably even easier than what I did. It parses a grub.conf file
and let's a user pick an entry.

Right now it just prints out what the user selected. I'm not sure how
it should integrate into the existing tools. Thoughts? Integrating it
shouldn't be pretty easy.

Note: It looks quite ugly in gnome-terminal. I'm sure there's a way to
handle the different term types better in curses. It looks just fine
though on a real terminal though.

Regards,

Anthony Liguori
Email: aliguori@us.ibm.com

Signed-off-by: Anthony Liguori
RE: [PATCH] Xen Grub-style boot loader [ In reply to ]
> It's a simple grub style ncurses application. This is my
> ncurses app so
> it's probably even easier than what I did. It parses a
> grub.conf file
> and let's a user pick an entry.

I think to be useful this would need to run within the guest domain such that the grub menu appeared over the guest console connection. We'd have to use something akin to a real bootloader (but 32bit) to pull in the image and jump at it. Using linux with a suitable initrd and kexec might be a good soloution.

I'm not sure that the interactive selection of kernels is the #1 requirement here -- I think its more about being able to read the kernel from the domain's file system, and to be able to control the command line options.

Ian


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Re: RE: [PATCH] Xen Grub-style boot loader [ In reply to ]
Ian Pratt wrote:
>>It's a simple grub style ncurses application. This is my
>>ncurses app so
>>it's probably even easier than what I did. It parses a
>>grub.conf file
>>and let's a user pick an entry.
>
>
> I think to be useful this would need to run within the guest domain such that the grub menu appeared over the guest console connection. We'd have to use something akin to a real bootloader (but 32bit) to pull in the image and jump at it. Using linux with a suitable initrd and kexec might be a good soloution.
>
> I'm not sure that the interactive selection of kernels is the #1 requirement here -- I think its more about being able to read the kernel from the domain's file system, and to be able to control the command line options.

I have some code for pulling in a Linux ELF image via UIP-TCP under
Xen1.3, unpacking it and jumping at it, if anyone is interested. The
total bootloader binary is 30kb.

The networking driver needs to be ported to Xen 2.0, but otherwise it
should just work.

Jacob


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Re: [PATCH] Xen Grub-style boot loader [ In reply to ]
Ian Pratt wrote:

>I think to be useful this would need to run within the guest domain such that the grub menu appeared over the guest console connection. We'd have to use something akin to a real bootloader (but 32bit) to pull in the image and jump at it. Using linux with a suitable initrd and kexec might be a good soloution.
>
>
Making the console appear over the guest connection isn't hard while
still having the boot loader be a dom0 process. It's particularly easy
if you make the console visible as a tty. In the current Xend
architecture, you would just dup the socket as the std(in|out) of the
process and exec the boot loader before starting the domain.

I think the only real advantage to having it be a part of domain-U is
that you avoid the problem with mounting a file system. The more I
think about it though the more of a security concerns worry me. Long
term, I think a domU loader is a better solution. However, I think
there's a large class of users where a dom0 boot loader would be just fine.

>I'm not sure that the interactive selection of kernels is the #1 requirement here -- I think its more about being able to read the kernel from the domain's file system, and to be able to control the command line options.
>
>
It's definitely not the #1 requirement but it's certainly useful. You
don't really need a boot loader to read the kernel from the domain's
file system or to give the user the ability to control the command line.

Would you being willing to accept a boot loader that ran as a dom0
process and exported it's screen through the console? Even if it was
only a temporary solution until a better boot loader was written? I ask
because I can probably code up the rest (I already can read the
grub.conf off of a specified device) by tonight or tomorrow.

I think it would take more time than I could invest to do the dom0
approach any time soon. Unless of course someone else is willing to do
it in which case I agree that the dom0 approach is superior :-)

Regards,
Anthony Liguori

>Ian
>
>
>



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Re: [PATCH] Xen Grub-style boot loader [ In reply to ]
Anthony Liguori wrote:

> It's a simple grub style ncurses application. This is my ncurses app
> so it's probably even easier than what I did. It parses a grub.conf
> file and let's a user pick an entry.
>
> Right now it just prints out what the user selected. I'm not sure how
> it should integrate into the existing tools. Thoughts? Integrating
> it shouldn't be pretty easy.

I'm sorry, my typing seems a bit off today. It should read, "This is my
first ncurses app" and "Integrating it should be pretty easy". I didn't
want anyone to think that it would be difficult to integrate :-)

Regards,
Anthony Liguori


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Re: Re: [PATCH] Xen Grub-style boot loader [ In reply to ]
On Thu, 2005-02-03 at 17:37 -0600, Anthony Liguori wrote:
> Would you being willing to accept a boot loader that ran as a dom0
> process and exported it's screen through the console? Even if it was
> only a temporary solution until a better boot loader was written? I ask
> because I can probably code up the rest (I already can read the
> grub.conf off of a specified device) by tonight or tomorrow.

I at least think that this would be an interesting point to start from.
And quite possibly interesting in a longer term.

Jeremy



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