Installation of Jekyll on Mac is usually less problematic than on Windows. However, you may run into permissions issues with Ruby that you must overcome. You should also use Bundler to be sure that you have all the required gems and other utilities on your computer to make the project run.
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Ruby and RubyGems

Ruby and RubyGems are usually installed by default on Macs. Open your Terminal and type which ruby and which gem to confirm that you have Ruby and Rubygems. You should get a response indicating the location of Ruby and Rubygems.

If you get responses that look like this:

/usr/local/bin/ruby

and

/usr/local/bin/gem

Great! Skip down to the Bundler section.

However, if your location is something like /Users/MacBookPro/.rvm/rubies/ruby-2.2.1/bin/gem, which points to your system location of Rubygems, you will likely run into permissions errors when trying to get a gem. A sample permissions error (triggered when you try to install the jekyll gem such as gem install jekyll) might look like this for Rubygems:

 >ERROR:  While executing gem ... (Gem::FilePermissionError)
  You don't have write permissions for the /Library/Ruby/Gems/2.0.0 directory.

Instead of changing the write permissions on your operating system’s version of Ruby and Rubygems (which could pose security issues), you can install another instance of Ruby (one that is writable) to get around this.

Install Homebrew

Homebrew is a package manager for the Mac, and you can use it to install an alternative instance of Ruby code. To install Homebrew, run this command:

/usr/bin/ruby -e "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/master/install)"

If you already had Homebrew installed on your computer, be sure to update it:

brew update

Install Ruby through Homebrew

Now use Homebrew to install Ruby:

brew install ruby

Log out of terminal, and then then log back in.

When you type which ruby and which gem, you should get responses like this:

/usr/local/bin/ruby

And this:

/usr/local/bin/gem

Now Ruby and Rubygems are installed under your username, so these directories are writeable.

Note that if you don’t see these paths, try restarting your computer or try installing rbenv, which is a Ruby version management tool. If you still have issues getting a writeable version of Ruby, you need to resolve them before installing Bundler.

Install the Jekyll gem

At this point you should have a writeable version of Ruby and Rubygem on your machine.

Now use gem to install Jekyll:

gem install jekyll

You can now use Jekyll to create new Jekyll sites following the quick-start instructions on Jekyllrb.com.

Installing dependencies through Bundler

Some Jekyll themes will require certain Ruby gem dependencies. These dependencies are stored in something called a Gemfile, which is packaged with the Jekyll theme. You can install these dependencies through Bundler. (Although you don’t need to install Bundler for this Documentation theme, it’s a good idea to do so.)

Bundler is a package manager for RubyGems. You can use it to get all the gems (or Ruby plugins) that you need for your Jekyll project.

You install Bundler by using the gem command with RubyGems:

gem install bundler

If you’re prompted to switch to superuser mode (sudo) to get the correct permissions to install Bundler in that directory, avoid doing this. All other applications that need to use Bundler will likely not have the needed permissions to run.

Bundler goes out and retreives all the gems that are specified in a Jekyll project’s Gemfile. If you have a gem that depends on other gems to work, Bundler will go out and retrieve all of the dependencies as well. (To learn more about Bundler, see About Ruby Gems.

The vanilla Jekyll site you create through jekyll new my-awesome-site doesn’t have a Gemfile, but many other themes (including the Documentation theme for Jekyll) do have a Gemfile.

Serve the Jekyll Documentation theme

  1. Browse to the directory where you downloaded the Documentation theme for Jekyll.
  2. Type jekyll serve
  3. Go to the preview address in the browser. (Make sure you include the / at the end.)