I switched the sources to Bullseye and the upgrade went smoothly, but when I do a full-upgrade, I get:

libc6-dev : Breaks: libgcc-8-dev (< 8.4.0-2~) but 8.3.0-6 is to be installed

My sources are as follows:

deb http://deb.debian.org/debian bullseye main
deb-src http://deb.debian.org/debian bullseye main

#deb http://deb.debian.org/debian buster-updates main
#deb-src http://deb.debian.org/debian buster-updates main

#deb http://security.debian.org/debian-security/ buster/updates main
#deb-src http://security.debian.org/debian-security/ buster/updates main

How can I fix this to finalize the upgrade?

P.S. I've looked at a recent issue here: Full-upgrade to Debian testing fails due to libc6-dev : Breaks: libgcc-8-dev

Which didn't help.


2 Answers 2


Debian 10 uses GCC 8, but Debian 11 currently uses GCC 9 (probably 10 by the time it’s released). For some reason, in your case, the upgrade fails to replace the GCC 8 packages, and the upgrade is blocked.

To fix this, remove gcc-8 and its dependencies.

This is a symptom of a more general problem with GCC libraries when upgrading from Debian 10 to testing; see Ryan Pavlik’s repository for a general solution and details of the problem, as well as links to bugs filed against GCC in the hope of an official fix.

  • 2
    That would remove 500+ packages. :( LANG=C sudo apt-get install gcc-8-base- libgcc-8-dev- polkit-kde-agent-1 kde-l10n-de libreoffice libqtcore4 ... The following packages have unmet dependencies: libqt5core5a : Breaks: libqtcore4 (< 4:4.8.7+dfsg-20~) but 4:4.8.7+dfsg-18 is to be installed E: Unable to correct problems, you have held broken packages.
    – MKesper
    Aug 25, 2020 at 7:02
  • @MKesper that indicates you have a bigger problem related to libqtcore4 and libqt5core5a, not gcc-8. Please ask a new question with the full details. Aug 25, 2020 at 7:08
  • 1
    I wonder if this is a general problem @StephenKitt, I'm seeing very similar symptoms as the OP here. Also on buster currently and it's more or less impossible to dist-upgrade to bullseye without removing a lot of stuff. :/ Dec 9, 2020 at 20:10
  • 1
    @PerLundberg yes, there is, see salsa.debian.org/rpavlik/gcc-10-compat for details... Dec 16, 2020 at 22:04
  • Thanks for that link @StephenKitt, I discovered that repo as well some days ago and used it successfully to upgrade one of my machines to bullseye. Great to get it linked from here. Dec 17, 2020 at 8:07

see previous, this updated link: Full-upgrade to Debian testing fails due to libc6-dev : Breaks: libgcc-8-dev

and this is what i did...

apt-get update
apt-get upgrade
apt-get -f upgrade
# or
apt full-upgrade -y

nothing works right?

this worked for me:

apt-get install aptitude
apt-get install libgcc-8-dev
apt-get update
apt-get install synaptic

but the worst happened after that.

went to home folder and every other folder and its all gone:

Unable to create io-slave. 
Error loading '/usr/lib/x86_64-linux-gnu/qt5/plugins/kf5/kio/file.so'."

I am not shutting down my pc because of this because i know i will not be able to boot back up i just have a feeling.

link: https://forum.manjaro.org/t/unable-to-create-io-slave-klauncher-said-error-loading-usr-lib-qt-plugins-kf5-kio-file-so/25866

also look at anon35400795 Jun '17

just restart (logout+login). That happens because Qt(Dolphin) loads this plugin, then you do an update and Qt conflicts the loadup of the new version, because its still holding the old version in RAM.

It worked for me!!!!

  • 1
    I’m not sure whether this is asking for help (because of all the folders which seem to have disappeared, although it’s not clear whether that’s just inside Dolphin) or explaining how to solve the problem in the question — if the latter, I’m dubious about advice which results in “every other folder and its all gone”... Aug 19, 2020 at 12:13
  • 1
    Saying that you fear being able to reboot and that your home directories are gone makes me believe that this is not an answer to the question. If you intended to claim that the 'restart (logout+login)' part solved the problem for you, perhaps that should be the extent of the answer, removing everything else.
    – Jeff Schaller
    Aug 19, 2020 at 13:34
  • I say that because the display manager is the top issue Of 2019-2020 with kali linux, i am fixing a lot of bugs so yes i fear some things because things break and I have to restore a clone hard drive to re engineer the fixes Aug 21, 2020 at 1:02
  • Everything worked for me, the only problem i have later is the kde gdm3 lightdm just switching and can’t login gui style login page because of the switching around of the gui display manager or just entirely the display manager not loading on boot. Aug 21, 2020 at 1:04

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .