I've gone through the process of migrating my previous Ubuntu server to a RedHat 6.x release. Contained in this article are the steps I had to go through in order to successfully install and configure the basics.

Installing Redmine on RedHat:
- Install MySQL
$ sudo yum -y install mysql mysql-server

- Install Apache Web Server
$ sudo yum -y install httpd

- Install development packages:
$ sudo yum -y install zlib-devel curl-devel openssl-devel httpd-devel apr-devel apr-util-devel mysql-devel

- Install Ruby
$ sudo curl -L https://get.rvm.io | bash -s stable --ruby

- Install Passenger
$ sudo gem install passenger
+ If there is an issue with invalid zlib library it is required to run:
sudo rvm reinstall all --force

- Install Bundler gem
$ sudo gem install bundler

- Install Apache passenger module
$ sudo passenger-install-apache2-module

- Restart Apache
$ sudo service httpd restart

- Create MySQL user and database:
$ mysql -u root -p
mysql> create user 'redmine'@'localhost' identified by 'redmine';
mysql> create database redmine;
mysql> grant all on redmine.* to 'redmine'@'localhost';
mysql> flush privileges;
mysql> exit

- Install/Configure Redmine:
$ cd /var/ww/html; svn co http://svn.redmine.org/redmine/branches/2.2-stable redmine-2.2
$ cd redmine-2.2
$ cat > config/database.yml<<EOF
production:
adapter: mysql
database: redmine
host: localhost
username: redmine
password: "redmine"
encoding: utf8
EOF

- Configure Rails:
+ bundler install --without development test postgresql sqlite zlib rmagick

- Redmine 2.2: Generate secret token:
$ sudo RAILS_ENV=production bundle exec rake generate_secret_token

- Create DB schema:
$ sudo RAILS_ENV=production bundle exec rake db:migrate

- Load default config data:
$ sudo RAILS_ENV=production bundle exec rake redmine:load_default_data