Bug#919029: grub-pc: meaningless message "RUB boot loader was previously installed..."

[Vincent Lefevre]

On 2019-01-12 13:33:35 +0000, Colin Watson wrote:
> On Sat, Jan 12, 2019 at 02:11:25PM +0100, Vincent Lefevre wrote:
> > On 2019-01-12 10:36:02 +0000, Colin Watson wrote:
> > > The ID changing is presumably the systemd bug you mentioned, and that
> > > seems to be the grave part of this.
> > 
> > Actually, I think that the fact that grub-pc changes the configuration
> > and loses the previous one is a grave bug too (even though it is
> > caused by the udev bug). There should have been a way for the user to
> > keep the previous configuration so that nothing gets broken due to
> > temporary issues.
> 
> I'm not at all sure that I agree.  The configuration in question exists
> in order to tell the postinst which devices it should run grub-install
> on.  If the device does not exist, it obviously isn't possible to run
> grub-install on it.
> 
> I can see the argument that it might be convenient to have configuration
> that effectively says "install to this device if it exists, otherwise
> continue anyway"; but such a configuration may mean that the GRUB image
> on disk that you might in fact attempt to boot from will end up being
> incompatible with the rest of /boot/grub/ and thus cause a failure to
> boot even though the postinst pretended everything is fine!
> Disregarding this kind of configuration error can have grave
> consequences of its own.  In any case, even if it might be convenient to
> have such a configuration, I won't accept that part of the issue as a
> grave bug.

I meant that the issue was that the user may not have remember
or even known where GRUB was installed (this was my case, and
I could find the information just because I keep track of the
changes of config.dat). This makes the problem unfixable without
risking to erase some data.

> Note that temporary issues of this kind are extremely rare; this is the
> first of its kind that I can recall hearing about.  By contrast, it's
> quite common for people to accidentally end up with a boot sector that
> they thought was being updated when it in fact wasn't.  It makes a lot
> more sense for the GRUB maintainer scripts to prioritise dealing with
> the latter situation than the former.  So I'm happy to try to improve
> the way the maintainer scripts responded here, but not in a way that
> results in silently ignoring missing devices.
> 
> If the dialog box hadn't been cut off in a way that made it non-obvious
> that GRUB needed you to select devices to install to, I don't think you
> would have ended up in this situation.

I don't think so. I think that I would have chosen to let the new
version of GRUB uninstalled for the moment (just like what I actually
did), because I did not know where to install it. Same loss of
information. The only difference would have been that the message
would have been clearer.

-- 
Vincent Lefèvre <vincent at vinc17.net> - Web: <https://www.vinc17.net/>
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Work: CR INRIA - computer arithmetic / AriC project (LIP, ENS-Lyon)