Control: tags -1 + confirmed On Fri, 2021-09-17 at 00:16 +0100, Colin Watson wrote: > https://bugs.debian.org/984533 and its clone > https://bugs.debian.org/985572 showed a buster-to-bullseye upgrade > bug in which debconf was unable to execute whiptail between unpacking > the new libslang2 and unpacking the new libc6. Part of the fix for > that involved adjusting debconf in bullseye to detect this situation > and gracefully fall back to text mode. The other part of the fix was > to adjust libc6.preinst to do something similar, in case debconf has > not yet been upgraded or the running debconf frontend is still from > an old version. > > Unfortunately, the code in libc6.preinst was somewhat broken, > resulting in buster-to-bullseye upgrades that hang in some > situations. We only noticed this after bullseye released because the > breakage is only apparent with certain package sets that provoke apt > into choosing particular upgrade orderings; even with this, I only > know of it happening for people who run "apt upgrade" as a separate > step before "apt full-upgrade" (IMO unnecessarily, but it seems to be > some people's habit). https://bugs.debian.org/994042 has an analysis > of the situation situation and a reproduction recipe. > > While fixing this particular upgrade bug requires fixing > libc6.preinst (because its broken logic happens before debconf has an > opportunity to decide what to do), it's possible for apt to attempt > to unpack some *other* package between unpacking the new libslang2 > and the new libc6 which also tries to use debconf in its preinst, and > that would run into a similar bug. (I admit to not having a concrete > example of such an upgrade ordering.) The only way to fix that > situation is to cherry- pick the fix for #985572 into debconf in > buster. As Aurelien points out in > #994042, we can't rely on people having applied all buster updates > before starting the upgrade to bullseye. Nevertheless, I think this > change would make upgrades more robust, since debconf must take great > care not to crash like this. >
Please go ahead; thanks. Regards, Adam
