I thought I could share my tips for moving a dozen PHP websites or so from one Virtualmin install on Ubuntu 8.04 LTS to Ubuntu 10.04 LTS. This covers only virtualmin Pro - I woudn’t know for the GPL version
configure your new server to your liking. Ubuntu 10 comes with PHP 5.3 so there will be some migration issues. Make sure to go through the master php.ini as you normally would and to modify all default settings to your typical installation.
restore virtual servers one by one, by doing a full backup from one server and restoring it on the new server. Then copy the php.ini config from /etc/php5/apache2/php.ini to /home/[website]/etc/php5/
PHP 5.3 forces PHPSESSID to be transmitted by cookies only. So that will be a problem for some of you. The solution is simple. Edit the default php.ini and make sure that “session.use_only_cookies = 1” is commented. This one has been giving me some major headaches when restoring backups.
Fix the suexec issue by editing /etc/apache2/mods-available/php5.conf and commenting the line “SetHandler application/x-httpd-php” – otherwise your websites will execute as www-data and not the virtual-server owner. NOTE: this should be fixed in new install scripts so you may not have to do this. So if you have the problem, this is the resolution. Then restart apache.
Edit the master proftpd config to add “DefaultHome ~” so that virtual server users are jailed in their /home/[user]. diretories when the FTP into the box
For me, those were the most important steps outside of the normal flow of things.