[Debconf-devel] Bug#845563: apt-get update which ends up in grub-probe loops near Stack.pm uninitialized value

[David Kalnischkies]

Control: reassign -1 debconf 1.5.56

(version number is a guess from the apt/stable version)

On Thu, Nov 24, 2016 at 04:45:35PM +0000, Graeme Vetterlein wrote:
> In brief. If I attempt to build a docker container using apt-get install , and that process kicks off a grub-probe. The probe
> fails (because we are in a container)  not a surprise. However this causes apt-get install to loop, presumably in the grub specific
> setup scripts.

apt has no "setup scripts" and no grub specific pieces. The packages
which are installed carry them with them (if any) and hence any bug with
them is a bug for them, not for the tool unfortunately enough to be
tasked with running them (= dpkg ← apt ← user).

So, reassigning to … debconf (which is another tool tasked by others
with doing stuff…) as "uninitialized value" sounds bad and I have no
idea if it is debconfs or grubs fault…


> yes | apt-get install --force-yes --allow-unauthenticated -y lttng-modules-dkms || echo "Ignore failure, hope that's OK"

Thanks for the nightmares tonight!

Really, that is some very scary commandline. Are you really sure that
you want (whatever package actually) so desperately that you completely
ignore security AND destroy your system (okay, its a container, but
still) for it? With destroying your system you might be able to live,
but I guess you want to use the container for something later on… bad if
an attacker has already infected it with rootkits due to that command.

Also, there are better ways to answer dpkg-conffile questions and to let
debconf pick the default option than to run 'yes' over them. I can't
give blank advice on that as it depends on what you want to do and stuff
but I would highly suggest looking into it! Some pointers:
DEBIAN_FRONTEND=noninteractive and dpkg --force-conf{new,old,def}.


Anway: On to the actual bug:

>  ... < elided>.....
> 
> debconf: falling back to frontend: Teletype
> 
> Creating config file /etc/default/grub with new version
> grub-probe: error: cannot find a device for / (is /dev mounted?).
> grub-probe: error: cannot find a device for /boot (is /dev mounted?).
> grub-probe: error: cannot find a device for /boot/grub (is /dev mounted?).
> Configuring grub-pc
> -------------------
> 
> You chose not to install GRUB to any devices. If you continue, the boot loader 
> may not be properly configured, and when this computer next starts up it will 
> use whatever was previously in the boot sector. If there is an earlier version 
> of GRUB 2 in the boot sector, it may be unable to load modules or handle the 
> current configuration file.
> 
> If you are already using a different boot loader and want to carry on doing so, 
> or if this is a special environment where you do not need a boot loader, then 
> you should continue anyway. Otherwise, you should install GRUB somewhere.
> 
> Continue without installing GRUB? 
> Use of uninitialized value $_[1] in join or string at /usr/share/perl5/Debconf/DbDriver/Stack.pm line 111.
> grub-probe: error: cannot find a device for / (is /dev mounted?).
> grub-probe: error: cannot find a device for /boot (is /dev mounted?).
> grub-probe: error: cannot find a device for /boot/grub (is /dev mounted?).
> Use of uninitialized value $_[1] in join or string at /usr/share/perl5/Debconf/DbDriver/Stack.pm line 111.
> You chose not to install GRUB to any devices. If you continue, the boot loader 
> may not be properly configured, and when this computer next starts up it will 
> use whatever was previously in the boot sector. If there is an earlier version 
> of GRUB 2 in the boot sector, it may be unable to load modules or handle the 
> current configuration file.
> 
> If you are already using a different boot loader and want to carry on doing so, 
> or if this is a special environment where you do not need a boot loader, then 
> you should continue anyway. Otherwise, you should install GRUB somewhere.
> 
> Continue without installing GRUB? 
> grub-probe: error: cannot find a device for / (is /dev mounted?).
> grub-probe: error: cannot find a device for /boot (is /dev mounted?).
> grub-probe: error: cannot find a device for /boot/grub (is /dev mounted?).
> Use of uninitialized value $_[1] in join or string at /usr/share/perl5/Debconf/DbDriver/Stack.pm line 111.
> You chose not to install GRUB to any devices. If you continue, the boot loader 
> may not be properly configured, and when this computer next starts up it will 
> use whatever was previously in the boot sector. If there is an earlier version 
> of GRUB 2 in the boot sector, it may be unable to load modules or handle the 
> current configuration file.
> 
> ....

That is why I am reassigning to debconf as it seems to loop with the
uninitialized variable, but that might also be due to a grub
maintainerscript… I don't know/haven't checked.

The original message contains a docker file with which it might be
reproducible, I just haven't quoted it to keep the mail relatively
manageable.


> gvetterlein at lyster:~/work/obsidian-1.0/infrastructure/HSPbuild$ cat 98localmirror 
> Acquire
> {
> 	Check-Valid-Until "false";
> }

Tip: Consider setting the option Acquire::Min-ValidTime with a high
enough value instead as that helps with figuring out then your local
mirror is hopelessly out of date/stale. If you don't get updates for
a month, that might be a very serious red flag…

You should also follow the manpage advice and append the label of the
repository to the option to have it not effect all your sources, but
just those with that label (l= in apt policy output).  btw: In stretch
you are able to just mark the sources line(s) for your local mirror(s)
directly with those options.


Best regards

David Kalnischkies
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