Ansible

Ansible is an open-source software platform for configuring and managing computers. It combines multi-node software deployment, ad hoc task execution, and configuration management. It manages nodes over SSH and requires Python (2.4 or later) to be installed on them. Modules work over JSON and standard output and can be written in any programming language. The system uses YAML to express reusable descriptions of systems.

Ansible is a DevOps tool for configuring, deploying, monitoring, and automating servers (among other things). This article will only discuss the Linux aspects. Most of the examples will use Vagrant. However, some of the examples/demos will include Rackspace, DigitalOcean, and Amazon's AWS as well.

Examples

Note: This article assumes you already have Vagrant and Ansible installed.

In the following examples, lines starting with "$" indicate a command to be run on the Ansible controlling machine (my laptop/local machine in most cases) and "[remote] $" indicates a command to be run on one of the nodes.

• Setup your local Ansible environment:

$ mkdir -p $HOME/dev/ansible
$ cd $HOME/dev/ansible
$ git init

• Create your inventory file and add it to your git repo (we will call our development group of hosts "dev"):

$ cat << EOF > hosts
[dev]
# Development host using a Ubuntu 14.04 vagrant box
192.168.1.10	ansible_ssh_user=vagrant
$ git add hosts

Note: The default inventory file lives at /etc/ansible/hosts. However, since I will be storing this file in my git repo, I like to keep it with the rest of my Ansible files.

• Ansible command syntax:

$ ansible <host-pattern> [-f forks] [-m module_name] [-a args]

• Test that you can communicate with your vagrant VM (I like to sometimes add "-vvvv" for extra verbosity whilst debugging/developing):

$ ansible dev -i hosts -u vagrant -vvvv -m command -a "cat /etc/issue"
10.11.1.103 | success | rc=0 >>
Ubuntu 14.04.2 LTS \n \l
$ ansible dev -i hosts -u vagrant -vvvv -m command -a "uptime"

Note: Since we defined our vagrant user in the inventory file ("hosts"), we no longer need to specify this user in the following examples. Also note that my vagrant box already has my SSH public key copied over (if not, make sure to add "-k" so Ansible prompts you for the password).

$ ansible dev -i hosts -m ping
10.11.1.103 | success >> {
    "changed": false, 
    "ping": "pong"
}

• Update your remote (vagrant VM, in this case) machine ("-s or "--sudo" to run operation with `sudo`):

$ ansible dev -i hosts -s -m command -a "apt-get update"

[remote] $ tailf /var/log/syslog
Jun 10 18:52:36 vagrant ansible-command: Invoked with executable=None shell=True args=apt-get update  removes=None creates=None chdir=None

• Get a list of "facts" about the vagrant VM:

Note: Ansible by default gathers "facts" about the machines under management, and these facts can be accessed in Playbooks and in templates. To see a list of all of the facts that are available about a machine, you can run the "setup" module as an ad-hoc action:

$ ansible dev -i hosts -m setup

This will print out a dictionary of all of the facts that are available for that particular host.

Using Ansible with Rackspace Cloud Servers

Note: See Category:Rackspace for more examples on how to interact with Rackspace's products and services.

• Create your Ansible development directory for Rackspace (this can, of course, be anywhere you like):

$ mkdir -p $HOME/dev/ansible/rax
$ cd $HOME/dev/ansible/rax

• Create your hosts inventory file:

$ cat << EOF > hosts
[localhost]
localhost ansible_connection=local
EOF

• Create your Rackspace API credentials file:

$ cat << EOF > ~/.raxpub
[rackspace_cloud]
username = <RAX_USERNAME>
api_key = <RAX_API_KEY>
EOF

• Create your Ansible playbook for creating a Rackspace Cloud Server:

$ cat << EOF > rax_server_create.yml
---
- name: Build a Rackspace Cloud Server
  hosts: localhost
  gather_facts: False
  tasks:
    - name: Server build request
      local_action:
        module: rax
        credentials: ~/.raxpub
        name: ansible-rax-test-1
        region: DFW # one of: http://www.rackspace.com/about/datacenters/
        flavor: general1-1 # "1 GB General Purpose v1"
        image: a743dd3b-e409-4833-be55-d85f6192817e # "Ubuntu 12.04 LTS (Precise Pangolin) (PVHVM)"
        key_name: my_rackspace_key # SSH key
        wait: yes
        state: present # CREATE
        networks:
          - private
          - public
      register: rax
EOF

• Run the above playbook to create your Rackspace Cloud Server:

$ ansible-playbook -vvvv -i hosts rax_server_create.yml

• Delete the above server:

$ sed -i 's/state: present/state: absent/' rax_server_create.yml
$ ansible-playbook -vvvv -i hosts rax_server_create.yml

A better method might be to create a separate playbook to delete a list of given Cloud Servers:

$ echo << EOF > rax_server_delete.yml
---
- name: Delete a list of Rackspace Cloud Servers
  hosts: localhost
  gather_facts: False
  tasks:
    - name: Server delete request
      local_action:
        module: rax
        credentials: ~/.raxpub
        region: ORD
        instance_ids: 959dbcaf-6145-4280-8206-78deaa364e4d,6eee1da0-a516-4059-828a-c0539a960324
        wait: yes
        state: absent # DELETE
      register: rax
EOF

$ ansible-playbook -vvvv -i hosts rax_server_delete.yml

Miscellaneous

• Disable `cowsay` (I _hate_ that this is not the default setting!):

$ sed -i 's/#\?nocows.*/nocows = 1/' /etc/ansible/ansible.cfg
#~OR~
$ ANSIBLE_NOCOWS=1 ansible-playbook -i hosts -s foo.yml
#~OR~ add the following to your .bashrc file:
export ANSIBLE_NOCOWS=1

See also

• Chef
• Puppet

External links

• Official website
• Official public code repository on GitHub
• List of Ansible Tutorials and Courses