update ruby in update guide

doc/update/6.9-to-7.0.md

@@ -13,7 +13,39 @@ sudo -u git -H bundle exec rake gitlab:backup:create RAILS_ENV=production
 sudo service gitlab stop
 ```
 
-### 2. Get latest code
+### 2. Update Ruby
+
+If you are still using Ruby 1.9.3 or below, you will need to update Ruby.
+You can check which version you are running with `ruby -v`.
+
+If you are you running Ruby 2.0.x, you do not need to upgrade ruby, but can consider doing so for performance reasons.
+
+If you are running Ruby 2.1.1 consider upgrading to 2.1.2, because of the high memory usage of Ruby 2.1.1.
+
+Install, update dependencies:
+
+```bash
+sudo apt-get install build-essential zlib1g-dev libyaml-dev libssl-dev libgdbm-dev libreadline-dev libncurses5-dev libffi-dev curl
+```
+
+Download and compile Ruby:
+
+```bash
+mkdir /tmp/ruby && cd /tmp/ruby
+curl --progress ftp://ftp.ruby-lang.org/pub/ruby/2.1/ruby-2.1.2.tar.gz | tar xz
+cd ruby-2.1.2
+./configure --disable-install-rdoc
+make
+sudo make install
+```
+
+Install Bundler:
+
+```bash
+sudo gem install bundler --no-ri --no-rdoc
+```
+
+### 3. Get latest code
 
 ```bash
 cd /home/git/gitlab
@@ -34,7 +66,7 @@ For GitLab Enterprise Edition:
 sudo -u git -H git checkout 7-0-stable-ee
 ```
 
-### 3. Update gitlab-shell (and its config)
+### 4. Update gitlab-shell (and its config)
 
 ```bash
 cd /home/git/gitlab-shell
@@ -42,7 +74,7 @@ sudo -u git -H git fetch
 sudo -u git -H git checkout v1.9.6
 ```
 
-### 4. Install libs, migrations, etc.
+### 5. Install libs, migrations, etc.
 
 ```bash
 cd /home/git/gitlab
@@ -64,7 +96,7 @@ sudo cp lib/support/init.d/gitlab /etc/init.d/gitlab
 sudo chmod +x /etc/init.d/gitlab
 ```
 
-### 5. Update config files
+### 6. Update config files
 
 #### New configuration options for gitlab.yml
 
@@ -74,12 +106,12 @@ There are new configuration options available for gitlab.yml. View them with the
 git diff 6-9-stable:config/gitlab.yml.example 7-0-stable:config/gitlab.yml.example
 ```
 
-### 6. Start application
+### 7. Start application
 
     sudo service gitlab start
     sudo service nginx restart
 
-### 7. Check application status
+### 8. Check application status
 
 Check if GitLab and its environment are configured correctly: