I upgraded my system to Debian 12, but I cannot login any more after I rebooted when the package installation seemed to be completed. The login prompt (on tty) tells me login incorrect after typing any (even empty, even root) string with my keyboard and finishing it with Return (standard way to type in a user name).
Sometimes the issue in comparable situations is because there's no space left on the device. I'm pretty sure I can exclude this as a possible reason here because I cheked that every partition has at least several MB of free space with gnome-disks from a live system.

The screen at Ctrl+Alt+F7 is stuck at [ OK ] Started Anonymizing overlay network for TCP. with a blinking underscore cursor in the line under the fullstop. The line breaks don't work correctly as it seems to add the space of a whole line to do the line break, not just breaking the line and starting at position 0 for writing the next line.

I'd like to not reinstall my system in order to use it again.

Ctrl+Alt+F1 as well as Ctrl+Alt+F3 behave in the same manner:

Debian GNU/Linux 12 hosti tty3

hosti login: root

Login incorrect
hosti login: _

I'd like to not need to reinstall Debian because I did lots of customisations, which I cannot list all anymore and therefore I'd looking forward to fixing my broken login (or system) way more than reinstalling the system.

EDIT Side observation: Trying to take an empty username for login doesn't succeed for the first attempt on the screen, but for the other ones. I also can only take four attempts "once"; the screen "clears" after the fifth attempt.

"Four attempts":

Debian GNU/Linux 12 hosti tty3

hosti login: number1

Login incorrect
hosti login: number2

Login incorrect
hosti login: number3

Login incorrect
hosti login: number4

Login incorrect
hosti login: numberFIVEwhichIStheLASToneSEENonTHEscreenAFTERthisONEtheSCREENseemsTOclearORrefreshAUTOMATICALLYafterEXAMININGtheATTEMPTtoLOGin_
  • are you saying that sometimes the error is "login incorrect" and sometimes the error is "no space left on the device" - but you see there's "some megabytes" free, so you just ignored this error - and what does I also can only take four attempts "once" mean? how does one do four attempts once? attempts at what? To be honest, I'd have updated 10->11 and then 11->12 .... you did backup your system before the upgrade, as recommended in every sane guide for upgrading major release Commented Jun 13, 2023 at 12:29
  • There is free disk space. Generally, a possible reason why a user cannot log into his system is because there's no space left on the device, which isn't the case on mine. I did do a backup for the $HOME, but nothing of the rest.
    – Nepumuk
    Commented Jun 13, 2023 at 12:59
  • OK, but login incorrect suggests you've typed in the wrong password Commented Jun 13, 2023 at 13:01
  • The thing is that I don't get to this point… I'm not prompted for a(ny) password.
    – Nepumuk
    Commented Jun 13, 2023 at 13:06
  • 1
    It certainly seems like the upgrade process did not complete successfully. Have you tried selecting "Advanced options for Debian GNU/Linux" in the GRUB boot menu, and then picking one of the (recovery mode) boot options? If that allows you to get into the system in command line mode, you should re-run apt full-upgrade to see if it reports things that still need to be upgraded.
    – telcoM
    Commented Aug 6, 2023 at 17:59

1 Answer 1


I have your identical same problem. I was at least able to access a terminal by adding -rw init=/bin/bash to the end of the line starting with “Linux“ on the Grub editing screen. Maybe from this point it is possible to do something.

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