I did a rsync clone of my LAMP stack folder running Mantis to a second virtual machine ( VM ). I made sure the clone worked in the VM, then I repeated upgrading Mantis on the VM until I got it right. Make sure you do a mysqldump before starting. I did both a normal and an XML version just in case.
/opt/lampstack-1.2-4/mysql/bin/mysqldump -uroot -p<passwdRoot> bitnami_mantis > ~/Desktop/bitnami_mantis.dump
/opt/lampstack-1.2-4/mysql/bin/mysqldump -uroot -p<passwdRoot> bitnami_mantis --xml > ~/Desktop/bitnami_mantis.xml
If needed, to restore a dump you can do something like.
./mysql -uroot -p<passwdRoot> bitnami_mantis < bitnami_mantis.dump
If you are a PHP app slacker like me, Bitnami makes it easy to set up a new server with their LAMP, MAMP, WAMP stacks and Mantis stack modules which is currently at version 1.2.10:http://bitnami.org/stack/mantis