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Old 09-21-2011, 05:48 PM
Matthew Garrett
 
Default grub / grub2 conflicts

On Wed, Sep 21, 2011 at 06:30:58PM +0100, Mark McLoughlin wrote:
> On Mon, 2011-09-19 at 20:11 +0100, Matthew Garrett wrote:
> > The grub package (as provided in Fedora) is not designed for that. This
> > would be a much easier discussion to have if you stopped describing
> > things that are manifestly true as "not true". And while it is the case
> > that grub *is* binary compatible between every version we've ever
> > released, it is *not* guaranteed that that remains true, or even that
> > it's true between us and any distribution that may be installed in a
> > guest.
>
> If libguestfs had code to detect that the guest version was incompatible
> and failed gracefully with a nice explanation for the user, then there's
> no problem right?

To be reliable you'd need to support disassembling the binaries
installed and working out what the arguments are meant to look like.
This doesn't seem like a great way to spend time. Remember that the
incompatibility isn't between libguestfs and the guest, it's between the
host grub and the guest grub. Both of those can change without
libguestfs's knowledge.

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Old 09-21-2011, 07:39 PM
Mark McLoughlin
 
Default grub / grub2 conflicts

On Wed, 2011-09-21 at 18:48 +0100, Matthew Garrett wrote:
> On Wed, Sep 21, 2011 at 06:30:58PM +0100, Mark McLoughlin wrote:
> > On Mon, 2011-09-19 at 20:11 +0100, Matthew Garrett wrote:
> > > The grub package (as provided in Fedora) is not designed for that. This
> > > would be a much easier discussion to have if you stopped describing
> > > things that are manifestly true as "not true". And while it is the case
> > > that grub *is* binary compatible between every version we've ever
> > > released, it is *not* guaranteed that that remains true, or even that
> > > it's true between us and any distribution that may be installed in a
> > > guest.
> >
> > If libguestfs had code to detect that the guest version was incompatible
> > and failed gracefully with a nice explanation for the user, then there's
> > no problem right?
>
> To be reliable you'd need to support disassembling the binaries
> installed and working out what the arguments are meant to look like.
> This doesn't seem like a great way to spend time.

Not your problem how libguestfs authors spend their time.

Nor whether they actually do this or choose to just warn their users
about potential incompatibility.

> Remember that the incompatibility isn't between libguestfs and the
> guest, it's between the host grub and the guest grub. Both of those
> can change without libguestfs's knowledge.

Sounds like we need a 'Conflicts: libguestfs' in both grub and grub2
then?

Cheers,
Mark.

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Old 09-21-2011, 07:42 PM
Matthew Garrett
 
Default grub / grub2 conflicts

On Wed, Sep 21, 2011 at 08:39:24PM +0100, Mark McLoughlin wrote:
> On Wed, 2011-09-21 at 18:48 +0100, Matthew Garrett wrote:
> > Remember that the incompatibility isn't between libguestfs and the
> > guest, it's between the host grub and the guest grub. Both of those
> > can change without libguestfs's knowledge.
>
> Sounds like we need a 'Conflicts: libguestfs' in both grub and grub2
> then?

I don't think so. Nothing they do or install conflicts with libguestfs.
libguestfs is simply trying to use them inappropriately.

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Old 09-21-2011, 07:54 PM
Peter Jones
 
Default grub / grub2 conflicts

On 09/21/2011 03:39 PM, Mark McLoughlin wrote:
> On Wed, 2011-09-21 at 18:48 +0100, Matthew Garrett wrote:
>> On Wed, Sep 21, 2011 at 06:30:58PM +0100, Mark McLoughlin wrote:
>>> On Mon, 2011-09-19 at 20:11 +0100, Matthew Garrett wrote:
>>>> The grub package (as provided in Fedora) is not designed for that. This
>>>> would be a much easier discussion to have if you stopped describing
>>>> things that are manifestly true as "not true". And while it is the case
>>>> that grub *is* binary compatible between every version we've ever
>>>> released, it is *not* guaranteed that that remains true, or even that
>>>> it's true between us and any distribution that may be installed in a
>>>> guest.
>>>
>>> If libguestfs had code to detect that the guest version was incompatible
>>> and failed gracefully with a nice explanation for the user, then there's
>>> no problem right?
>>
>> To be reliable you'd need to support disassembling the binaries
>> installed and working out what the arguments are meant to look like.
>> This doesn't seem like a great way to spend time.
>
> Not your problem how libguestfs authors spend their time.
>
> Nor whether they actually do this or choose to just warn their users
> about potential incompatibility.
>
>> Remember that the incompatibility isn't between libguestfs and the
>> guest, it's between the host grub and the guest grub. Both of those
>> can change without libguestfs's knowledge.
>
> Sounds like we need a 'Conflicts: libguestfs' in both grub and grub2
> then?

Yes, but this will hardly help the situation, which right now is that the
distro pulls in grub 2, because that's what we've collectively chosen to do,
and libguestfs pulls in grub on the host, even though it isn't really using
it there. So effectively your solution is to keep the problem we've got
right now.

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Old 09-21-2011, 08:10 PM
"Richard W.M. Jones"
 
Default grub / grub2 conflicts

On Wed, Sep 21, 2011 at 03:54:28PM -0400, Peter Jones wrote:
> Yes, but this will hardly help the situation, which right now is that the
> distro pulls in grub 2, because that's what we've collectively chosen to do,
> and libguestfs pulls in grub on the host, even though it isn't really using
> it there. So effectively your solution is to keep the problem we've got
> right now.

Tools on the host are often useful in guest situations.

If I created a filesystem using mke2fs:

lvcreate /dev/vg/foo
mke2fs /dev/vg/foo

and attached this to a guest, is that an inappropriate use of host
tools for a guest?

Rich.

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Old 09-21-2011, 08:28 PM
Matthew Garrett
 
Default grub / grub2 conflicts

On Wed, Sep 21, 2011 at 09:10:06PM +0100, Richard W.M. Jones wrote:
> On Wed, Sep 21, 2011 at 03:54:28PM -0400, Peter Jones wrote:
> > Yes, but this will hardly help the situation, which right now is that the
> > distro pulls in grub 2, because that's what we've collectively chosen to do,
> > and libguestfs pulls in grub on the host, even though it isn't really using
> > it there. So effectively your solution is to keep the problem we've got
> > right now.
>
> Tools on the host are often useful in guest situations.
>
> If I created a filesystem using mke2fs:
>
> lvcreate /dev/vg/foo
> mke2fs /dev/vg/foo
>
> and attached this to a guest, is that an inappropriate use of host
> tools for a guest?

Yes, if the guest is running a sufficiently old kernel. But mke2fs is
designed to allow you to create filesystems that will work with
arbitrary kernels, so it's possible to use it in appropriate ways. grub
is not designed to be compatible across arbitrary versions, and so using
it with that expectation is inappropriate.

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Old 09-22-2011, 10:27 AM
Mark McLoughlin
 
Default grub / grub2 conflicts

On Wed, 2011-09-21 at 15:54 -0400, Peter Jones wrote:
> On 09/21/2011 03:39 PM, Mark McLoughlin wrote:
> > On Wed, 2011-09-21 at 18:48 +0100, Matthew Garrett wrote:
> >> Remember that the incompatibility isn't between libguestfs and the
> >> guest, it's between the host grub and the guest grub. Both of those
> >> can change without libguestfs's knowledge.
> >
> > Sounds like we need a 'Conflicts: libguestfs' in both grub and grub2
> > then?
>
> Yes, but this will hardly help the situation, which right now is that the
> distro pulls in grub 2, because that's what we've collectively chosen to do,
> and libguestfs pulls in grub on the host, even though it isn't really using
> it there. So effectively your solution is to keep the problem we've got
> right now.

Sigh. I was joking. Obviously, if maintainers went around inserting
Conflicts with other packages because they don't like how the other
package works, then there'd be an order of magnitude more unpleasantness
on fedora-devel.

Not liking the way libguestfs works is no justification for an arbitrary
grub2 Conflicts in the grub package.

It sounds like there are issues which necessitate the Conflicts - e.g.
the grubby issue - but that they could be resolved. Can we focus on
those issues, what exactly they are and how folks can do to help resolve
them?

Cheers,
Mark.

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Old 09-22-2011, 01:05 PM
Matthew Garrett
 
Default grub / grub2 conflicts

On Thu, Sep 22, 2011 at 11:27:35AM +0100, Mark McLoughlin wrote:

> Sigh. I was joking. Obviously, if maintainers went around inserting
> Conflicts with other packages because they don't like how the other
> package works, then there'd be an order of magnitude more unpleasantness
> on fedora-devel.

The grub maintainer is telling you that the way in which you're trying
to use grub is broken. You *need* to use the grub files that are in
guest, not the host. This will be even more true with grub 2. It's not a
matter of disliking the approach, it's a matter of it being demonstrably
technically incorrect.

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Old 09-22-2011, 03:50 PM
Mark McLoughlin
 
Default grub / grub2 conflicts

On Thu, 2011-09-22 at 14:05 +0100, Matthew Garrett wrote:
> On Thu, Sep 22, 2011 at 11:27:35AM +0100, Mark McLoughlin wrote:
>
> > Sigh. I was joking. Obviously, if maintainers went around inserting
> > Conflicts with other packages because they don't like how the other
> > package works, then there'd be an order of magnitude more unpleasantness
> > on fedora-devel.
>
> The grub maintainer is telling you that the way in which you're trying
> to use grub is broken. You *need* to use the grub files that are in
> guest, not the host. This will be even more true with grub 2. It's not a
> matter of disliking the approach, it's a matter of it being demonstrably
> technically incorrect.

There's nothing technically incorrect about the approach, demonstrably
or otherwise, if the version of grub in the guest and host is
compatible.

Cheers,
Mark.

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Old 09-22-2011, 04:00 PM
Matthew Garrett
 
Default grub / grub2 conflicts

On Thu, Sep 22, 2011 at 04:50:16PM +0100, Mark McLoughlin wrote:
> On Thu, 2011-09-22 at 14:05 +0100, Matthew Garrett wrote:
> > The grub maintainer is telling you that the way in which you're trying
> > to use grub is broken. You *need* to use the grub files that are in
> > guest, not the host. This will be even more true with grub 2. It's not a
> > matter of disliking the approach, it's a matter of it being demonstrably
> > technically incorrect.
>
> There's nothing technically incorrect about the approach, demonstrably
> or otherwise, if the version of grub in the guest and host is
> compatible.

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.

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