To add ANOTHER redmine instance on the same machine:
====================================================
Author: A. Palladino
Date:  08 Feb 2011


This is not the most elegant way, but it was the least time consuming.
This assumes you have followed the instructions in instr_redmine_install.txt
and have ROOT privileges on the host machine.

The additional instance of redmine will be for the xxx experiment. In my case, I made
them for the nab and npdg experiments. So I had "nab" in place of "xxx" in the instructions
below.


===First edit /etc/httpd/conf.d/redmine.conf to have the new balancer and rewrite rule:===


  <Proxy balancer://xxx_redmine_cluster>
    Order allow,deny
    Allow from all
    BalancerMember http://127.0.0.1:8101
    BalancerMember http://127.0.0.1:8102
    BalancerMember http://127.0.0.1:8103
  </Proxy>


  RewriteRule ^/xxx_cms(.*)$ balancer://xxx_redmine_cluster%{REQUEST_URI} [P,QSA,L]


============================================================================================




The simplest way for me to do this was to copy the whole redmine install directory 
to redmine_0.8.7_xxx, preserving ownership and permissions!

[root@anton ~]# cd /opt/
[root@anton /opt]# cp -rp redmine-0.8.7 redmine-0.8.7_xxx
[root@anton /opt]# 

Now create a new database for the new experiment's CMS:

[root@anton /opt]# mysql -u root -p
Enter password:
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 11
Server version: 5.0.77 Source distribution

Type 'help;' or '\h' for help. Type '\c' to clear the buffer.

mysql> create database xxx_redmine character set utf8;
Query OK, 1 row affected (0.03 sec)

mysql> 
mysql> quit
Bye



Now if the copying is finished,
[root@anton /opt]# cd  redmine-0.8.7_xxx
[root@anton redmine-0.8.7_xxx]# kwrite config/database.yml &
===rename===
production -> xxx_production
===and===
database: production -> database: xxx_production


===Edit the environment.rb file to have the correct new relative path for the URL====
[root@anton redmine-0.8.7_xxx]# gedit config/environment.rb
Redmine::Utils::relative_url_root = "/xxx_cms"
ActionController::AbstractRequest.relative_url_root = "/xxx_cms"


[root@anton redmine-0.8.7_xxx]# cd config/environments
[root@anton redmine-0.8.7_xxx]# mv production.rb xxx_production.rb
[root@anton redmine-0.8.7_xxx]# rake config/initializers/session_store.rb
[root@anton redmine-0.8.7_xxx]# rake db:migrate RAILS_ENV="xxx_production"
[root@anton redmine-0.8.7_xxx]# rake redmine:load_default_data RAILS_ENV="xxx_production"
[root@anton redmine-0.8.7_xxx]# gedit config/email.yml &
===Then edit it so:===
production:
  delivery_method: :sendmail
===becomes===
xxx_production:
  delivery_method: :sendmail


Now configure the cluser. Select new ports that you haven't used before!
For PEN  CMS I used 3 ports, starting at 8001, 8002, 8003.
For NAB  CMS I used 3 ports, starting at 8101, 8102, 8103.
For NPDg CMS I used 3 ports, starting at 8201, 8202, 8203.

[root@anton redmine-0.8.7_xxx]# mongrel_rails cluster::configure -e xxx_production -p 8101 -N 3 -c /opt/redmine-0.8.7_xxx --prefix /xxx_cms


[root@anton redmine-0.8.7_xxx]# ln -s /opt/redmine-0.8.7_xxx/config/mongrel_cluster.yml /etc/mongrel_cluster/xxx_redmine.yml


=====Now we're ready to start redmine with the mongrel cluster :-)  !!! =====

[root@anton redmine-0.8.7_xxx]# mongrel_rails cluster::start
[root@anton redmine-0.8.7_xxx]# service httpd restart




===************=====
Some notes from which I have adapted the method. They are not exact, and will not work directly.
http://www.redmine.org/boards/2/topics/1019
http://www.redmine.org/boards/2/topics/1262