If you're on a Debian based installation, before you install rvm, you need to
install a system Ruby and then install build-essentials.
So, to install some requirements, run:
# aptitude update
# aptitude upgrade
# aptitude install ruby build-essential openssl libreadline6 libreadline6-dev curl git-core zlib1g zlib1g-dev libssl-dev libyaml-dev libsqlite3-dev sqlite3 libxml2-dev libxslt-dev autoconf libc6-dev ncurses-dev automake libtool bison subversion pkg-config
Then, it boils down to installing rvm by using this command:
$ curl -L https://get.rvm.io | bash -s stable --ruby
Read instructions carefully as this process requires compilation of Ruby and related utilities. Also, if you install RVM before executing the command to install its dependencies, make sure to reinstall the Ruby by doing:
$ rvm reinstall default
Now, you have to make sure rvm runs when your shell is started. This step is actually outlined in the rvm installation process, but, just append this to your .bashrc:
[[ -s "~/.rvm/scripts/rvm" ]] && source "~/.rvm/scripts/rvm"
You can do that easily using this command:
echo '[[ -s "~/.rvm/scripts/rvm" ]] && source "~/.rvm/scripts/rvm"' >> ~/.bashrc
Okay, so Ruby's installed, but now you need to install bundler, a package manager for Ruby with this:
$ gem install bundler
Whew. Now, go to the project root and do a:
$ bundle install
If that all worked, then you can proceed to run the server using:
$ middleman server
If you want to generate the HTML files, go ahead and do a:
$ middleman build
Which will create a /build directory in the root and populate it.