As ownCloud 9.1.1 was shipped the apt-key got replaced and the old one is not valid anymore, which in other words means that you can’t update ownCloud through apt-get anymore. The fix for this is very easy and done in just a few simple steps. Open a terminal and write these commands:

  1. sudo apt-key list
  2. sudo apt-key del [OWNCLOUD KEY NUMBER]
  3. sudo wget -nv -O Release.key
  4. sudo apt-key add - < Release.key

Now the key is replaced and you should be able to update ownCloud through apt-get. If you run the ownCloud VM just run this command:

sudo bash /var/scripts/