Install (RedHat CentOS Fedora)

Install ruby 1.9.2

Become root

su - 

Make sure you have the prerequisite packages

yum install git-core curl sqlite sqlite-devel
yum groupinstall "Development Tools" "Development Libraries"

Download, extract and build Ruby 1.9

cd /opt
wget http://ftp.ruby-lang.org/pub/ruby/1.9/ruby-1.9.2-p290.tar.gz
tar xfvz ruby-1.9.2-p290.tar.gz
cd ruby-1.9.2-p290
./configure
make
make install

Download, extract and install RubyGems

cd /opt
wget http://production.cf.rubygems.org/rubygems/rubygems-1.8.10.tgz
tar xzvf rubygems-1.8.10
ruby setup.rb

If you already have rubygems, upgrade to latest version

gem update --system

We don't want to download documentation

echo "gem: --no-rdoc --no-ri" > ~/.gemrc

Install Gitosis

It will create a profile 'gitosis:git' on your system

yum install gitosis
adduser -r -s /bin/sh -c 'git version control' -U -m git

ssh-keygen -t rsa

sudo -H -u git gitosis-init < ~/.ssh/id_rsa.pub
sudo chmod 755 /home/git/repositories/gitosis-admin.git/hooks/post-update

Install GitLab

cd /home
git clone git://github.com/gitlabhq/gitlabhq.git
cd gitlabhq/

Install this library first

yum install python-pygments
gem install bundler
bundle 

Note: If you get issues with installing gems see: http://stackoverflow.com/questions/3605235/rails-3-passenger-cant-find-git-gems-installed-by-bundler

Prepare the database

bundle exec rake db:setup RAILS_ENV=production

# create admin user 
# [email protected]
# pass.....5iveL!fe
bundle exec rake db:seed_fu RAILS_ENV=production

or as daemon

rails s -e production -d