bug#35996: User account password got locked when booting old generation

[Ludovic Courtès]

Hi Florian,

"pelzflorian (Florian Pelz)" <address@hidden> skribis:

> On Sat, Jun 01, 2019 at 11:37:51PM +0200, Ludovic Courtès wrote:
>> This is definitely not a problem when booting.  It could be a problem if
>> you’re concurrently running ‘guix system reconfigure’ (which runs
>> activation snippets, including the account updating code) and some other
>> program, such as ‘passwd’, that assumes it holds an exclusive lock on
>> the file.  Though in that case, the worst that could happen is that the
>> changes made by Guix would be undoed by that other program.

Actually, another thing that could happen is that Guix reads an
incomplete /etc/shadow because some other program is writing to it.

In that case, suppose Guix reads a partial /etc/shadow where user
“florian” is missing.  It would then create a new /etc/shadow where the
password for “florian” is uninitialized (or set to the initial value
that appears in config.scm.)

Could it be what happened to you?  You’d have to be running ‘passwd’ or
‘usermod’ or whatever at exactly the same time as ‘guix system
reconfigure’ (and you’d have to be “lucky”).

> I also tried running this script:
>
> #!/run/current-system/profile/bin/bash
> MD5=$(sudo md5sum /etc/shadow)
> echo "Current /etc/shadow has md5sum: $MD5"
> until [ "$(sudo md5sum /etc/shadow)" != "$MD5" ]; do
>     sudo guix system roll-back
>     sudo guix system reconfigure /etc/config.scm
> done
> notify-send "/etc/shadow changed!" "Maybe I reproduced the issue."

The code in (gnu build accounts) is purely functional and deterministic,
so you have no chance of getting a different /etc/shadow with this
script, unless perhaps you concurrently run ‘passwd’ or similar.

> error: 
> '/gnu/store/h5bi85lgnpqcjx2avy126lwiss01idsj-grub-efi-2.02/sbin/grub-install 
> --boot-directory //boot --bootloader-id=Guix --efi-directory //boot/efi' 
> exited with status 1; output follows:
>
>   Installing for x86_64-efi platform.
>   Could not prepare Boot variable: No such file or directory
>   
> /gnu/store/h5bi85lgnpqcjx2avy126lwiss01idsj-grub-efi-2.02/sbin/grub-install: 
> error: efibootmgr failed to register the boot entry: Input/output error.

Maybe you’ve exhausted the room for those EFI “variables” or something?

Thanks for your debugging work!

Ludo’.