The beta3 update for owncloud 6 is available. Here is how to install it manually.

Download the update on your owncloud server

pi@raspberrypi ~ $  wget http://download.owncloud.org/community/testing/owncloud-6.0.0beta3.zip

pi@raspberrypi ~ $  unzip owncloud-6.0.0beta3.zip

Create a backup of the files and database

pi@raspberrypi ~ $  mkdir owncloud_bkp

pi@raspberrypi ~ $  sudo rsync -a /var/www/owncloud/ /home/pi/owncloud_bkp/

pi@raspberrypi ~ $  mysqldump owncloud -u root -p > /home/pi/owncloud.sql

Copy the update

pi@raspberrypi ~ $  sudo rsync –inplace -rtv owncloud/ /var/www/owncloud/

Visiting the webinterface of your installation will complete the update.