Install Ruby, Ruby gems, and Chef-client

Mac OSX

Install X-Code from Mac Appstore
Open Xcode and do the following :  Xcode >> Preferences >> Downloads >> Command Line Tools
$ cd /tmp
$ curl -O http://production.cf.rubygems.org/rubygems/rubygems-1.8.24.tgz
$ tar zxf rubygems-1.8.24.tgz
$ cd rubygems-1.8.24
$ ruby setup.rb –no-format-executable
$ sudo gem install chef

CentOS6

$ yum -y install ruby ruby-devel ruby-ri ruby-rdoc ruby-shadow gcc gcc-c++ automake autoconf make curl dmidecode git
$ cd /tmp
$ curl -O http://production.cf.rubygems.org/rubygems/rubygems-1.8.24.tgz
$ tar zxf rubygems-1.8.24.tgz
$ cd rubygems-1.8.24
$ ruby setup.rb –no-format-executable
$ sudo gem install chef

Ubuntu

$ apt-get install -y curl git ruby1.9.1 rubygems1.9.1 chef

This is the key that allows you to authenticate yourself as an admin user to the chef server
Chef requires an existing admin to authorize a new admin
$ scp root@chef-server:/etc/chef/webui.pem  /etc/chef/webui.pem

Run Knife Configure

$ knife configure -i
Example Output:

Overwrite /root/.chef/knife.rb? (Y/N) y
Please enter the chef server URL: [http://chef-server:4000] http://chef-server:4000
Please enter a clientname for the new client: [root] jtran
Please enter the existing admin clientname: [chef-webui]
Please enter the location of the existing admin client's private key: [/etc/chef/webui.pem]
Please enter the validation clientname: [chef-validator]
Please enter the location of the validation key: [/etc/chef/validation.pem]
Please enter the path to a chef repository (or leave blank):
Creating initial API user...
Created client[jtran]
Configuration file written to /root/.chef/knife.rb

Verify Knife is working

$ knife client list
Example Output:

  jtran
  chef-webui
  chef-validator