Re: Important information regarding upcoming dpkg 1.16.2 upload

[Raphael Hertzog <hertzog@debian.org>]

Hello,

For people who have been playing with multiarch and are scared by
Guillem's (uncoordinated) announce, I have written a small script
to detect whether you have been affected by one of the theoretical
problems that Guillem diagnosed (you only need libdpkg-perl and perl).

If it outputs nothing on your system, then you're fine. Otherwise
it should give you some instructions to follow to bring it back to a
coherent state.

On Sat, 10 Mar 2012, Guillem Jover wrote:
> With those dpkg versions, when installing a M-A:same instance of
> package P arch A, when a previous non-M-A:same version of package P
> arch B was present in a config-files state, the installation would
> incorrectly remove the control files on the infodb for the arch B
> instance. You should check for any packages in the status db w/o
> matching files under /var/lib/dpkg/info/.

The script checks for this but dpkg would already output a warning
anyway ("files list file for package `%.250s' missing, assuming
package has no files currently installed.").

> Another effect of the bogus in-core db layout affected the disappearing
> logic, so if you have been running any such dpkg versions, you should
> also check in the logs that no package has been improperly disappeared,
> although the installed files should still be present.

I don't check this but dpkg prints an explicit message about disappearance
of packages and AFAIK a normal apt-get upgrade should never trigger the
case where a package can be improperly disappeared. It was only seen when
trying to replace a package by its foreign counterpart which was not
really allowed in the first place.

Checking your dpkg logs doesn't hurt though.

> upgrading, you should either downgrade to a non-multiarch enabled dpkg, or
> make sure there's no package present (i.e. with status >= config-files)
> with a mix of M-A:same and non-M-A:same instances.

The script verifies that any package with multiple instances are correctly
marked as Multi-Arch: same.

Cheers,
-- 
Raphaël Hertzog ◈ Debian Developer

Pre-order a copy of the Debian Administrator's Handbook and help
liberate it: http://debian-handbook.info/liberation/

#!/usr/bin/perl

use Dpkg::Control;
use Dpkg::Index;

my $arch = `dpkg --print-architecture`;
chomp($arch);

my $status = Dpkg::Index->new(type => CTRL_FILE_STATUS);
$status->load("/var/lib/dpkg/status");

sub find_foreign {
    my $a = shift;
    return ($a ne $arch and $a ne "all");
}

# Detect multiple instances which are not M-A: same
foreach my $foreign ($status->get("Architecture" => &find_foreign)) {
    my $pkg = $foreign->{'Package'};
    my $pkgarch = $foreign->{'Package'} . ':' . $foreign->{'Architecture'};
    my $ma = $foreign->{'Multi-Arch'};

    print "INFO: Foreign package detected: $pkgarch (Multi-Arch: $ma)\n";

    my @pkgs = $status->get("Package" => $pkg);
    if (scalar(@pkgs) > 1) {
	foreach my $item (@pkgs) {
	    $pkgarch = $item->{'Package'} . ':' . $item->{'Architecture'};
	    if ($item->{'Multi-Arch'} ne "same") {
		print "PROBLEM: one instance of $pkg is not Multi-Arch: same";
		print "SOLUTION: dpkg -P $pkgarch";
	    }
	}
    }
}

# Find broken packages
foreach my $pkg ($status->get()) {
    my $ma = $pkg->{'Multi-Arch'} || '';
    next if ($pkg->{'Status'} =~ m/ not-installed$/);

    my $pkgarch = $pkg->{'Package'};
    if ($ma eq "same") {
	$pkgarch = $pkg->{'Package'} . ':' . $pkg->{'Architecture'};
    }

    if (! -e "/var/lib/dpkg/info/$pkgarch.list") {
	print "PROBLEM: $pkgarch has missing info files\n";
	print "SOLUTION: apt-get --reinstall install $pkgarch\n";
    }
}