KVM and Kernel Development

KVM and Kernel Development

[Slohm Gadaburi]

Hi all,

I want to use KVM for kernel development of modern kernels.

It looks like the best thing is to build the kernel on the host,
and then do something like:
kvm guest.img -kernel /path/to/new/kernel -append "root=...
console=ttyS0" -nographic
to test it. hopefully the guest will boot straight into a texual
login.

Unfortunately I can't get it to work with modern
distributions. I installed 64bit Hardy as a guest,
but I failed to get it to boot with an external kernel
(I did gave it an initramfs drive using the initrd option,
and set the kernel root param to the right UUID number).
Besides, I really don't need the graphics and I couldn't
find a way to make Ubuntu start in text mode (no init levels
in Ubuntu anymore..).

Any ideas ? What's the best practice for kernel development with KVM ?
do you have the perfect guest for that ? maybe even there's
a ready image somewhere to download ?

I need a modern, 64-bit distribution that I can easily produce
a bootable kernel for it, preferably without initrd stuff, and i don't
need graphics...

Thanks for the help,
Slohm.

Re: KVM and Kernel Development

[Soren Hansen]

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On Tue, Jul 01, 2008 at 12:12:22PM +0300, Slohm Gadaburi wrote:
> Unfortunately I can't get it to work with modern distributions. I
> installed 64bit Hardy as a guest, but I failed to get it to boot with
> an external kernel (I did gave it an initramfs drive using the initrd
> option, and set the kernel root param to the right UUID number).

I've done this loads of times with great success. What happens when you
try?

> Besides, I really don't need the graphics and I couldn't find a way to
> make Ubuntu start in text mode (no init levels in Ubuntu anymore..).

Just pass "single" on the kernel command line, and you'll end up in
single user mode.

-- 
Soren Hansen               | 
Virtualisation specialist  | Ubuntu Server Team
Canonical Ltd.             | http://www.ubuntu.com/

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Re: KVM and Kernel Development

[Slohm Gadaburi]

Hi Soren,

> I've done this loads of times with great success. What happens when you
> try?

It hangs with:

* Running local boot scripts (/etc/rc.local)   [OK]

> Just pass "single" on the kernel command line, and you'll end up in

Yeah, that works - I can get the root shell, but I really need a fully
functional multi-user system. Something like what used to be init
level 3. Do you think there's a way to reach that with Ubuntu ? As a
last resort I guess I can use the standard graphics mode, but that's
so uncomfortable comparing to a textual mode.

Less importantly, but still interesting, do you think I can boot Hardy
without an initramfs ?

Thanks a lot for the assitance!
Slohm
>
> --
> Soren Hansen               |
> Virtualisation specialist  | Ubuntu Server Team
> Canonical Ltd.             | http://www.ubuntu.com/
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Re: KVM and Kernel Development

[Soren Hansen]

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On Tue, Jul 01, 2008 at 01:00:04PM +0300, Slohm Gadaburi wrote:
> > I've done this loads of times with great success. What happens when
> > you try?
> It hangs with:
> 
> * Running local boot scripts (/etc/rc.local)   [OK]

That's hardly what I call failing to boot... Did you look at the other
virtual terminals.

>> Just pass "single" on the kernel command line, and you'll end up in
> Yeah, that works - I can get the root shell, but I really need a fully
> functional multi-user system. Something like what used to be init
> level 3. Do you think there's a way to reach that with Ubuntu ? As a
> last resort I guess I can use the standard graphics mode, but that's
> so uncomfortable comparing to a textual mode.

If you don't want a GUI, just don't install one?

> Less importantly, but still interesting, do you think I can boot Hardy
> without an initramfs ?

You're doing this to do kernel development, right?  So you wouldn't be
using the hardy kernels anyway.

-- 
Soren Hansen               | 
Virtualisation specialist  | Ubuntu Server Team
Canonical Ltd.             | http://www.ubuntu.com/

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Re: KVM and Kernel Development

[Slohm Gadaburi]

On Tue, Jul 1, 2008 at 1:32 PM, Soren Hansen <soren@ubuntu.com> wrote:
> On Tue, Jul 01, 2008 at 01:00:04PM +0300, Slohm Gadaburi wrote:
>> * Running local boot scripts (/etc/rc.local)   [OK]
>
> That's hardly what I call failing to boot... Did you look at the other
> virtual terminals.

I tried "sendkey alt-f1" or "sendkey ctrl-alt-f1" (or f2) to no avail...
didn't get any prompt..(hitting enter a few times does not help)
Any other way to get to the virtual terminals ?

> If you don't want a GUI, just don't install one?

Can I do that with a standard desktop cd or must I use the alternate cd ?

> You're doing this to do kernel development, right?  So you wouldn't be
> using the hardy kernels anyway.

my bad. I assumed there's some user space fs magic that is built into
that initramfs.

Thank you for the assistance. It really helps !
Slohm

Re: KVM and Kernel Development

[Soren Hansen]

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replied off-list as I don't think this is of general interest to the kvm
community.

-- 
Soren Hansen               | 
Virtualisation specialist  | Ubuntu Server Team
Canonical Ltd.             | http://www.ubuntu.com/

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Re: KVM and Kernel Development

[Slohm Gadaburi]

On Tue, Jul 1, 2008 at 6:32 PM, Soren Hansen <soren@ubuntu.com> wrote:
> replied off-list as I don't think this is of general interest to the kvm
> community.

Thanks for the help both on and off-list.

(if anyone's interested: the problem was indeed a lack of getty
running on /dev/ttyS0)

Re: KVM and Kernel Development

[Eric Van Hensbergen]

On Tue, Jul 1, 2008 at 5:00 AM, Slohm Gadaburi <slohmg@gmail.com> wrote:
> Hi Soren,
>
>> I've done this loads of times with great success. What happens when you
>> try?
>
> It hangs with:
>
> * Running local boot scripts (/etc/rc.local)   [OK]
>

Sounds like you don't have getty running on ttyS0.

           -eric