[Freedombox-discuss] lost sudo after apt-get upgrade

[preexo@googlemail.com (Tim Mohrbach)]

Hi all,

I ran an upgrade today, haven?t done any in a few months before. Done it with apt-get update and apt-get upgrade via ssh inside a screen with root user.
It ran very well and I rebooted my box afterwards. Since then I lost sudo access on my user, which is quite concerning. Also plinth is not working anymore. 

tim at freedombox:~$ sudo su
[sudo] password for tim: 
tim is not in the sudoers file.  This incident will be reported.

Anyone an idea how I can get myself some sudo access again? -_- 
Thanks for any help in advance!
Best regards
Tim