If you run a TKLBAM backup of your existing server and then restore it to a new instance of the v12.0 appliance hopefully it'll just work. Having said that there may be some tweaking required (depends on the changes made to the software between the version included on v11.x and the version included on v12.0). Personally I wouldn't destroy your existing instance/appliance until you are sure all is well...

If it doesn't all work as expected then I would check for any Redmine docs on upgrading from the version in v11 to the version in v12 (check the TKL Redmine appliance page to see which versions are included in each).

I guess it's probably even better to do that homework first if you are keen (although it's not the way I usually do things! :D).

It'd be great if you document your experience (this thread is as good a place as any) even if it fails and you can't work out why or how to fix it, at least we'll know there is an issue and we can look at how to resolve it.

I upgraded from 11.2 to 12.0.  I used TKLBAM.  I experienced the following problems with corresponding fixes:

Problem: SSH stopped working after the restore of the backup.

Cuase: When the restore was done and the packages were updated the old files in /etc from the restore were left untouched.  This is becuase the package intentionally doesn't upgrade these files if it thinks they have been modified.  The problem with that is that they were still the old files from Ubuntu.  So when you tried to start SSH it was looking for the upstart related files.  These are present on Squeeze by default.

Resolution:

cd /etc/ssh

tar -cvf * ~/ssh.backup.tar

sudo apt-get remove openssh-server openssh-client ssh

sudo dpkg --purge openssh-server openssh-client ssh

sudo apt-get install ssh

cd /etc/ssh

tar -xvf ~/ssh.backup.tar

This restored all of the files from the package.

Problem: redmine couldn't connect to the database

Cuase: The redmine user was not in the database

Resolution:

create the redmine user in the database with these instructions( http://dev.mysql.com/doc/refman/5.1/en/create-user.html )  making sure to create the user as 'redmine'@'localhost'

Set the users password ( http://dev.mysql.com/doc/refman/5.1/en/set-password.html )

Grant the user access to the databases( http://dev.mysql.com/doc/refman/5.1/en/grant.html )

After the restore there were 6 databases:

Old Databases from my restore

railsapp_development
railsapp_production
railsapp_test

New databases from the new versoin

redmine_development 
redmine_production  
redmine_test 

Edit /var/www/redmine/config/database.yml and change the password in all three places ( found an example here http://www.tutorialspoint.com/ruby-on-rails/rails-database-setup.htm )

Restart as needed

Problem: None of my old database was showing up in Redmine

Cuase: /var/www/redmine/config/database.yml was pointing to the wrong database

Resolution:

Changed redmine_* to railsapp_*

Problem:  Couldn't login after fixing all of the changes above

Cause: Not sure I undestand on this one but found a thread on the redmine forums that said to do the steps below.( http://www.redmine.org/boards/2/topics/24762 )

Resolution:

As root I did the following:

cd /var/www/redmine

rake db:migrate RAILS_ENV=production
rake db:migrate_plugins RAILS_ENV=production

I hope this helps someone else.