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Old 09-22-2011, 06:44 PM
David Airlie
 
Default grub / grub2 conflicts

> On Thu, Sep 22, 2011 at 02:02:15PM -0400, David Airlie wrote:
>
> > you run rpm -q grub in the guest and on the host, if they are the
> > same nvr,
> > then they are the same package, where's the rocket science here.
>
> No, that's not good enough. You need to know the version installed on
> the system, not the packaged version. Upgrading the package doesn't
> cause grub-install to be rerun.
>
> > > There is no rational reason to have grub and grub2 installed on
> > > the
> > > same
> > > system at once, and having them both there increases the
> > > complexity
> > > of
> > > the system.
> >
> > you can install KDE and GNOME and you are worrying about grub and
> > grub2?
>
> They don't both attempt to sit in the same few bytes.

Nicely editing out of the other use-case I supplied. grub and grub2 *packages* don't install into the same few bytes.

I thought you were good at backing up arguments with technical reasons, not strawmen.

The argument is "should it be possible to install grub1 and grub2 *packages* on the same system?"

The strawman is if you install grub1 and grub2 bootloaders into the MBR on the same system they will conflict. I totally agree with your strawman, but you still haven't provided any technical reasons why the argument is wrong. Above all people Matthew I thought you were aware of how strawmen work and would be against their use.

Dave.
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Old 09-22-2011, 06:45 PM
Jesse Keating
 
Default grub / grub2 conflicts

On Sep 22, 2011, at 11:18 AM, Peter Jones wrote:
> On 09/22/2011 02:02 PM, David Airlie wrote:
>>
>>> On Thu, Sep 22, 2011 at 05:18:09PM +0100, Mark McLoughlin wrote:
>>>> On Thu, 2011-09-22 at 17:00 +0100, Matthew Garrett wrote:
>>>>> grub provides no mechanism for you to know that, which means you
>>>>> can't
>>>>> reliably know that. Which means relying on them being compatible
>>>>> is
>>>>> incorrect.
>>>>
>>>> You described yourself how libguestfs could check it. And failing
>>>> libguestfs doing it, the user could be warned to check it.
>>>
>>> I described something that is, practically speaking, impossible.
>>
>> you run rpm -q grub in the guest and on the host, if they are the same nvr,
>> then they are the same package, where's the rocket science here.
>
> The whole point of libguestfs's usage was that the package isn't actually
> installed in the guest. So that won't work.
>
> The rest of your point ignores that grub1 is going away as soon as is
> reasonably practicable.


It also ignores any non-rpm guests.

- jlk


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Old 09-22-2011, 06:47 PM
"Richard W.M. Jones"
 
Default grub / grub2 conflicts

On Thu, Sep 22, 2011 at 11:38:26AM -0700, Adam Williamson wrote:
> On Thu, 2011-09-22 at 17:18 +0100, Mark McLoughlin wrote:
>
> > You described yourself how libguestfs could check it. And failing
> > libguestfs doing it, the user could be warned to check it.
>
> 'check' it? And what's the user expected to do if they're incorrect?
> Crowbar Ubuntu's grub2 into Fedora, or vice versa, so the host and the
> guest will be compatible?

We don't pretend to work on Ubuntu grub2, never said we did.

> I hate to say it, but honestly, this thread looks pretty clear-cut to an
> outsider: pjones and mjg59 are correct, and you and rwmj are incorrect.
> Their arguments that it is fundamentally unsafe to use the host's grub
> or, even more so, grub2 in a guest have clear merit, and it honestly
> feels like the counter-arguments so far have been 'we've got away with
> it so far' and 'doing it any other way is hard, and we already wrote all
> this code, so please stop raising inconvenient questions'. Neither of
> those arguments are at all compelling. I haven't seen a single serious
> attempt to refute the central point that there is no guarantee of
> compatibility between any particular two versions or even builds of grub
> or grub2, and there is not even a mechanism for denoting and testing
> compatibility. Given this, it's hard to see how it can possibly be the
> right thing to do to use the host's grub or grub2 in the guest.

The issue here isn't this at all.

Issue #1 is that a conflicts was added to grub2, but no reason is
given. It was apparently done to work around some problem in grubby,
but again there's no clarity on what the problem(s) were and if there
would be a better way to fix this.

There is a further issue #2, quite orthogonal, which is that grub
(upstream) doesn't support offline installation. This is a bug in
grub 1 & 2 which really should be taken upstream. Nevertheless, it's
quite possible to use grub1 offline on compatible guests. We don't
really need to "prove" this, because we do it, and test the results,
and we publish everything we do in open source code.

Rich.

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Old 09-22-2011, 06:51 PM
"Richard W.M. Jones"
 
Default grub / grub2 conflicts

On Thu, Sep 22, 2011 at 11:45:11AM -0700, Jesse Keating wrote:
> On Sep 22, 2011, at 11:18 AM, Peter Jones wrote:
> > On 09/22/2011 02:02 PM, David Airlie wrote:
> >>
> >>> On Thu, Sep 22, 2011 at 05:18:09PM +0100, Mark McLoughlin wrote:
> >>>> On Thu, 2011-09-22 at 17:00 +0100, Matthew Garrett wrote:
> >>>>> grub provides no mechanism for you to know that, which means you
> >>>>> can't
> >>>>> reliably know that. Which means relying on them being compatible
> >>>>> is
> >>>>> incorrect.
> >>>>
> >>>> You described yourself how libguestfs could check it. And failing
> >>>> libguestfs doing it, the user could be warned to check it.
> >>>
> >>> I described something that is, practically speaking, impossible.
> >>
> >> you run rpm -q grub in the guest and on the host, if they are the same nvr,
> >> then they are the same package, where's the rocket science here.
> >
> > The whole point of libguestfs's usage was that the package isn't actually
> > installed in the guest. So that won't work.
> >
> > The rest of your point ignores that grub1 is going away as soon as is
> > reasonably practicable.
>
>
> It also ignores any non-rpm guests.

Guys ...

libguestfs can inspect any guest and work out what apps are installed,
what OS there is, what arch, what bootloader etc. We support a dozen
different Linux distros (not just rpm/deb-based but some really odd
ones too), along with FreeBSD, and Windows.

We really have thought about all of this.

Rich.

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Old 09-22-2011, 06:51 PM
Peter Jones
 
Default grub / grub2 conflicts

On 09/22/2011 02:41 PM, Richard W.M. Jones wrote:
> On Thu, Sep 22, 2011 at 02:18:48PM -0400, Peter Jones wrote:
>> On 09/22/2011 02:02 PM, David Airlie wrote:
>>>
>>>> On Thu, Sep 22, 2011 at 05:18:09PM +0100, Mark McLoughlin wrote:
>>>>> On Thu, 2011-09-22 at 17:00 +0100, Matthew Garrett wrote:
>>>>>> grub provides no mechanism for you to know that, which means you
>>>>>> can't
>>>>>> reliably know that. Which means relying on them being compatible
>>>>>> is
>>>>>> incorrect.
>>>>>
>>>>> You described yourself how libguestfs could check it. And failing
>>>>> libguestfs doing it, the user could be warned to check it.
>>>>
>>>> I described something that is, practically speaking, impossible.
>>>
>>> you run rpm -q grub in the guest and on the host, if they are the same nvr,
>>> then they are the same package, where's the rocket science here.
>>
>> The whole point of libguestfs's usage was that the package isn't actually
>> installed in the guest. So that won't work.
>
> This is not correct, grub is installed in the guest, but we don't want
> to run it from the guest because of security problems. I outlined it
> in an earlier email in this thread.

Oh, my mistake. That being beside the point, it pretty much means any VM
created in a previous OS release won't work. In any case I totally disagree
with your idea of security, as I mentioned at the time. It makes things worse,
not better.

And that's still ignoring that grub1 needs to completely go away.

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Old 09-22-2011, 06:58 PM
Matthew Garrett
 
Default grub / grub2 conflicts

On Thu, Sep 22, 2011 at 02:44:00PM -0400, David Airlie wrote:

> Nicely editing out of the other use-case I supplied. grub and grub2 *packages* don't install into the same few bytes.
>
> I thought you were good at backing up arguments with technical reasons, not strawmen.
>
> The argument is "should it be possible to install grub1 and grub2 *packages* on the same system?"
>
> The strawman is if you install grub1 and grub2 bootloaders into the MBR on the same system they will conflict. I totally agree with your strawman, but you still haven't provided any technical reasons why the argument is wrong. Above all people Matthew I thought you were aware of how strawmen work and would be against their use.

Because it means additional complexity for any tools which have to
interact with the bootloader and provides no benefit for any real
usecases.

--
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Old 09-22-2011, 07:07 PM
Adam Williamson
 
Default grub / grub2 conflicts

On Thu, 2011-09-22 at 19:47 +0100, Richard W.M. Jones wrote:

> > I hate to say it, but honestly, this thread looks pretty clear-cut to an
> > outsider: pjones and mjg59 are correct, and you and rwmj are incorrect.
> > Their arguments that it is fundamentally unsafe to use the host's grub
> > or, even more so, grub2 in a guest have clear merit, and it honestly
> > feels like the counter-arguments so far have been 'we've got away with
> > it so far' and 'doing it any other way is hard, and we already wrote all
> > this code, so please stop raising inconvenient questions'. Neither of
> > those arguments are at all compelling. I haven't seen a single serious
> > attempt to refute the central point that there is no guarantee of
> > compatibility between any particular two versions or even builds of grub
> > or grub2, and there is not even a mechanism for denoting and testing
> > compatibility. Given this, it's hard to see how it can possibly be the
> > right thing to do to use the host's grub or grub2 in the guest.
>
> The issue here isn't this at all.

It's become that.

> Issue #1 is that a conflicts was added to grub2, but no reason is
> given. It was apparently done to work around some problem in grubby,
> but again there's no clarity on what the problem(s) were and if there
> would be a better way to fix this.

It seems pretty clear that the thread kinda diverged away from the
actual question of the conflict several days ago, and is now
fundamentally about whether it's correct for libguestfs to expect to be
able to use the host bootloader package to configure the guest's
bootloader. If you are actually accepting that it's incorrect for
libguestfs to do this, but maintaining that the conflict is not valid,
you could do a better job of making that clear, and directing the
argument back to the issue of the conflict.

It's certainly tenable for you to hold that, even if you accept that
your example use case for having both grub and grub2 installed at the
same time (libguestfs) is not a good one for technical reasons, it's
still not necessary or correct for the grub and grub2 packages to
conflict. That's a viable path to go down. But it's not at all clear
from the thread that that's actually what you're doing.

> There is a further issue #2, quite orthogonal, which is that grub
> (upstream) doesn't support offline installation. This is a bug in
> grub 1 & 2 which really should be taken upstream. Nevertheless, it's
> quite possible to use grub1 offline on compatible guests. We don't
> really need to "prove" this, because we do it, and test the results,
> and we publish everything we do in open source code.

Again, your argument is 'we've gotten away with it so far', which was
true of every bad idea ever at *some* point. You can get away with
driving on the wrong side of the street for quite a long time, if you
pick a pretty quiet street; it doesn't make it the right thing to do.

It may be that, if you raised it with the grub team, they would accept
that offline installation using a different version of the code is
something they would like to attempt to support. If so, great, everyone
will be happy. But it doesn't change the fact that, at present, this is
not supported, and libguestfs is doing the wrong thing by relying on it
and hoping to carry on getting away with it.
--
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Old 09-22-2011, 07:23 PM
Miloslav Trmańć
 
Default grub / grub2 conflicts

On Thu, Sep 22, 2011 at 8:40 PM, Matthew Garrett <mjg59@srcf.ucam.org> wrote:
> On Thu, Sep 22, 2011 at 07:38:54PM +0100, Richard W.M. Jones wrote:
>> On Thu, Sep 22, 2011 at 05:37:39PM +0100, Matthew Garrett wrote:
>> We allow you to inspect the guest to find the OS version, and even
>> versions of individual packages installed in it.
>
> The package version of grub does nothing to tell you which version of
> grub is actually installed in the boot sector.

That doesn't matter: When libguestfs runs its installation of grub,
the boot sector will be overwritten. What matters is the versions of
stage1/1.5/2 files in the guest, which is adequately described by
identifying the RPM.
Mirek
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Old 09-22-2011, 07:27 PM
"Richard W.M. Jones"
 
Default grub / grub2 conflicts

On Thu, Sep 22, 2011 at 02:51:40PM -0400, Peter Jones wrote:
> Oh, my mistake. That being beside the point, it pretty much means
> any VM created in a previous OS release won't work. In any case I
> totally disagree with your idea of security, as I mentioned at the
> time. It makes things worse, not better.

Not running random code from untrusted guests makes things worse?

> And that's still ignoring that grub1 needs to completely go away.

It's not going to completely go away until such guests completely go
away. People use virtualization precisely because it allows them to
continue to run very old operating systems. Or even supported ones
like RHEL 6 (using grub1 until 2017-2020).

Rich.

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Old 09-22-2011, 07:33 PM
"Richard W.M. Jones"
 
Default grub / grub2 conflicts

On Thu, Sep 22, 2011 at 07:58:35PM +0100, Matthew Garrett wrote:
> On Thu, Sep 22, 2011 at 02:44:00PM -0400, David Airlie wrote:
>
> > Nicely editing out of the other use-case I supplied. grub and grub2 *packages* don't install into the same few bytes.
> >
> > I thought you were good at backing up arguments with technical reasons, not strawmen.
> >
> > The argument is "should it be possible to install grub1 and grub2 *packages* on the same system?"
> >
> > The strawman is if you install grub1 and grub2 bootloaders into the MBR on the same system they will conflict. I totally agree with your strawman, but you still haven't provided any technical reasons why the argument is wrong. Above all people Matthew I thought you were aware of how strawmen work and would be against their use.
>
> Because it means additional complexity for any tools which have to
> interact with the bootloader and provides no benefit for any real
> usecases.

That grubby has to decide whether to run grub or grub2?

Please can you outline exactly what bugs arose that caused the
conflicts to be added. THIS is what we've been asking for.

If we can fix those bugs in a better way, we can remove the conflicts,
and we can take over legacy maintainership of grub1 ourselves.

Rich.

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