Ansible for Configuration Management and IT automation

Wow, Ansible is a great tool for configuration management and IT automation. I got this reference from here and here.

1. Install ansible on your workstation (machine which will be the controller)
$ sudo yum install ansible
$ ansible --version

2. Create env variable
$ export ANSIBLE_HOSTS=~/ansible/ansible_hosts

3. Create hosts file
$ echo -e "perf-c690\nperf-c691" > ~/ansible/ansible_hosts

4. Do a quick ping
$ ansible all -m ping --ask-pass

5. Now, let's create ssh keys
(Should typically run using your own user account, have used root here for convenience) 
# ssh-keygen -t rsa

6. Copy public key to the remote machines
$ ansible all -m copy -a "src=/root/.ssh/id_rsa.pub dest=/tmp/id_rsa.pub" --ask-pass -c paramiko

Warning: error message: "Aborting, target uses selinux but python bindings (libselinux-python) aren't installed!"
Which means we need to install libselinux-python on the remote machine prior to copying the files there. We can use ansible to do that for us.

Install libselinux-python on remote machines
$ ansible all -m yum -a "name=libselinux-python state=latest" -u root --ask-pass -c paramiko

Now we can go back to copying the public key

7. Let's add the public key to the remote machines
$ ansible all -m shell -a "cat /tmp/id_rsa.pub >> /root/.ssh/authorized_keys" --ask-pass -c paramiko

8. Test if we actually don't need any password
$ ansible all -m shell -a "hostname"

9. Now we can do or install whatever on the remote machines, let's try installing expect
$ ansible all -m yum -a "name=expect state=latest" -u root

10. We can remotely reboot all machines at once
$ ansible all -a "/sbin/reboot" -u root

Install Ruby via RVM on CentOS 6.5

Got install from here.
RVM best practices here.
How to use RVM gemsets here.
How to use Bundler here.

1. Install pre-requisites
# yum groupinstall -y development

2. Install RVM
# curl -L get.rvm.io | bash -s stable

3. Create system environment for RVM
# source /etc/profile.d/rvm.sh

4. Install Ruby
# rvm reload
# rvm install 2.2.1

5. Check version of ruby installed
# ruby --version

6. To see all rubies installed
# rvm list rubies
rvm rubies
=* ruby-2.2.1 [ x86_64 ]
# => - current
# =* - current && default
#  * - default

7. To set a Ruby version as the default
# rvm use 2.2.1 --default
Using /usr/local/rvm/gems/ruby-2.2.1

8. Shortcut - create a new gemset along with a fresh .rvmrc in our project directory
# cd projects/dev/phoenix
# rvm --rvmrc --create use 2.2.1@phoenix
ruby-2.2.1 - #gemset created /usr/local/rvm/gems/ruby-2.2.1@phoenix
ruby-2.2.1 - #generating phoenix wrappers..........
Using /usr/local/rvm/gems/ruby-2.2.1 with gemset phoenix

9. To ignore rmvrc warnings ...
# rvm rvmrc warning ignore all.rvmrcs

10. Now when we cd to our project directory we get a confirmation which ruby-version and gemset we are using...
dev]# cd phoenix/
Using: /usr/local/rvm/gems/ruby-2.2.1@phoenix

11. Let's make use of bundler to make it easy to track and install the exact gems and versions for our project
# gem install bundler

12. Create a Gemfile
# bundle init
Writing new Gemfile to /root/projects/dev/phoenix/Gemfile

13. Add gems to Gemfile
# vi Gemfile
source "https://rubygems.org"
# 1. de facto XML/HTML parsing library
gem 'nokogiri'

14. Now, let's install all gems we listed in the Gemfile
# bundle install

To create and use gemsets the longer way:
a. Create gemset
# rvm gemset create my_proj

b. Use the gemset
# rvm gemset use my_proj

c. Install a gem
# gem install package_name

d. Wipe all gems installed
# rvm gemset empty my_proj

e. Delete the gemset
# rvm gemset delete my_proj

f. Check your current gemset
# rvm gemset name