Creating a Gallery2 virtual site
Prepare the virtualhost by creating a directory /home/sites/www.sitename.ext/site/gallery for the gallery files and giving it the correct permissions (chown razor:group /home/sites/www.sitename.ext/site/gallery/) NB owner must be razor at this time, because he can access the gallery2 installation files (due to suPHP)
Also create a directory for the gallery data /home/sites/www.sitename.ext/g2data. Chown razor:group this directory as well.
Go to the Virtual site Installer at http://gallery2.tripany.com/install/
Log in to Tripghost, cd /usr/share/gallery2
In the install you will recieve a string, which must be pasted in to /usr/share/gallery2/login.txt to authenticate.
Choose a Multisite Installation and enter the path in the first step.
When it gets to the database setup, I've put all the galleries into one database: gallery2. Every user gets their own specific table and column prefixes, so remember to enter them as well!
Then it's mainly a whole load of clicking untill you get to the modules. Here, deactivate GD under the graphics toolkits because it eats a LOT of memory!
Go to http://www.sitename.ext/site/gallery/main.php and log in, go to site admin (top right) and then modules (left bar). Configure URL Rewrite. Choose PHP Path Info and save. Then in the modules list, 'activate' URL Rewrite.
ImageMagick won't activate because it's not installed.
For more information, the documentation is here: http://codex.gallery2.org/Category:Gallery_2:Installation