WordPress can be updated in the site-admin. However, in some setups it does not work and has to be done manually. It goes like this:
1. Backup Database (get login-data out of wp-config.php) to a file “olsen.sql”
mysqldump -u olsen -p -h mysql5.vmk.zhdk.ch olsen >../../olsen.sql
2. Get and unpack latest wordpress. Be careful, the unpacking will create a directory “wordpress”. If you have already an existing installation in a folder with the same name, it will be overwritten.
wget wordpress.org/latest.tar.gz tar -xvf latest.tar.gz
3. Copy content and config to the new installation
cp -R eisdieler/wp-content/* wordpress/wp-content/ cp eisdieler/wp-config.php wordpress/
4. Rename the old installation, replace the old one by the new one by renaming it
cp -R eisdieler/wp-content/* wordpress/wp-content/ cp -R eisdieler/wp-config.php wordpress/
5. Set the permissions, so that the user and the webserver have the required access
chown -R olsen eisdieler chgrp -R www-data eisdieler chmod -R 775 eisdieler
6. Login to the site-admin. The database will be updated.