Can not perform `pod install` under el capitan (15A279b)

Installing CocoaPods on OS X 10.11

These instructions were tested on all betas and the final release of El Capitan.

Custom GEM_HOME

This is the solution when you are receiving the "Operation not permitted" error.

$ mkdir -p $HOME/Software/ruby
$ export GEM_HOME=$HOME/Software/ruby
$ gem install cocoapods
[...]
1 gem installed
$ export PATH=$PATH:$HOME/Software/ruby/bin
$ pod --version
0.38.2

I had to update the system before 'gem install' otherwise I got this:

ERROR: Error installing cocoapods: activesupport requires Ruby version >= 2.2.2.:

Here's what worked for me:

gem update --system
sudo gem install -V -n /usr/local/bin cocoapods
pod install

I actually needed to just update:

pod update

Solution, fix for Cocoapods error on El Capitan 10.11:

sudo gem install -n /usr/local/bin cocoapods

You previously opened Xcode under root access.

Just delete /Pods/Pods.xcodeproj/xcuserdata/root.xcuserdatad folder and continue pod install