Prerequisites
Linux
Packages:
- git
- python
- python-devel
- python-pip
- openssl
- ansible
Installation and Configuration
Linux
Be sure to install epel-release first and then update your caches (if CentOS). On Ubuntu/Debian distributions, you may install from the default repositories. Assuming CentOS, as in our course, do the following:
sudo yum install git python python-devel python-pip openssl ansible
User Accounts
Create a user called ansible (example) on the server you intend to use Ansible to run playbooks from AND each of the Ansible nodes you intend to run playbooks on. Set the user as a sudo-capable user and include the NOPASSWD: ALL directive in /etc/sudoers.
Create an SSH key with ssh-keygen on the Ansible server. Exchange that key using ssh-copy-id on each of the nodes you are running playbooks on. This allows the playbook to run with escalated privileges as needed.
Configuration Files
- /etc/ansible/ansible.cfg
- Primary Ansible configuration file (agentless, daemon-less configuration, read on each ansible command run)
- Uncomment “inventory” field
- Uncomment “become user” field
- /etc/ansible/hosts
- Copy original to /etc/ansible/hosts.original
- Create one or more sections with group names, sample below
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[local] localhost [web] webserver1 webserver2 [db] dbserver1 dbserver2 |
Running Arbitrary Commands
Format
Arbitrary commands can be run against hosts or groups of hosts at the command line, one at a time. In order to list the contents of the home directory for the ansible user, for example:ansible GROUPNAME -a “ls -al /home/ansible”
ansible GROUPNAME -a "ls -al /home/ansible"
Running a command that requires sudo privileges should not be run with the sudo command, but rather the sudo parameter in the ansible command itself, like so:ansible GROUPNAME -s -a “ls -al /var/log/messages”
ansible GROUPNAME -s -a "ls -al /var/log/messages"
You can also execute a single module against one or more hosts at the command line by using the module parameter. As an example:ansible GROUPNAME -s -m yum -a “name=httpd state=latest”
ansible GROUPNAME -s -m yum -a "name=httpd state=latest"
Test if all machines in your inventory respond to a ping request:
ansible all -m ping
YAML Structure for Playbooks
Sample Playbook with Major Sections
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--- # COMMENT ABOUT PLAYBOOK - hosts: hostsToRunAgainst remote_user: ansible become: yes become_method: sudo connection: ssh gather_facts: no vars: var1: value var2: value tasks: - name: Some description of what we are doing yum: name: httpd state: latest notify: - startservice handlers: - name: startservice service: name: httpd state: restarted |
Quick Notes
ansible-playbook
- Calling a playbook ansible-playbook /path/to/playbook.yaml
Inventory
- /etc/ansible/hosts
- Defines nodes/groups of nodes to operate against
- $ANSIBLE_HOSTS
- Shell variable containing one or more ansible hosts
