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Ansible examples of configuration files.

Contents:

• Start
• Ansible playbooks and tasks
• Host file
• Output
• Privilege escalation
• Boto 3 - The AWS SDK for Python

Start

Verify Ansible runs and its version is at least 2.1:

$ ansible --version
2.1.0.0

Run a simple command:

$ ansible all -i localhost, -c local -m shell -a 'echo hello world'
localhost | SUCCESS | rc=0 >>
hello world

Clone this repo and go into it:

$ git clone https://github.com/sixarm/sixarm_ansible_examples
$ cd //github.com/sixarm/sixarm_ansible_examples

Ansible playbooks and tasks

This repository is oriented toward playbooks and tasks.

See the playbooks directory and tasks directory.

One playbook corresponds to one task. This is because Ansible currently can run one playbook, but cannot run one task without a playbook.

Run a simple playbook:

$ ansible-playbook -i localhost, -c local playbooks/hello-world.yml

PLAY [Hello World] ***********************************************************

TASK [setup] *******************************************************************
ok: [localhost]

TASK [include] *****************************************************************
included: tasks/hello-world.yml for localhost

TASK [Hello World] ***********************************************************
ok: [localhost] => {
  "msg": "Hello World"
}

PLAY RECAP *********************************************************************
localhost                  : ok=3    changed=0    unreachable=0    failed=0

Host file

We typically use a host file, even when we are simply doing command line one-off scripts, because we like to have the flexibility of using multiple hostnames and multiple settings.

Create a host file with this text:

localhost

Now you can use the host file like this:

$ ansible-playbook -i host -c local playbooks/hello-world.yml

Output

Ansible does not print the result of commands. Instead, an Ansible script can register a variable that receives the output, and then a subsequent task can print the output by using the debug module.

Example task:

- name: demo
  command: which python
  register: x
- debug: var=x.stdout_lines

Run a playbook to print the current python interpreter path:

$ ansible-playbook -i host -c local playbooks/which-python.yml
…
ok: [localhost] => {
    "x.stdout_lines": [
        "/usr/local/bin/python"
    ]
}

Privilege escalation

Ansible documentation strongly recommends against setting any sudo password in plaintext, and instead using the command line option --ask-become-pass abbreviated -K. This option used to be called --ask-sudo-pass.

Run a playbook that uses the "become" setting, which does privilege escalation akin to the sudo command:

$ ansible-playbook -K -i host -c local playbooks/demo-become.yml
SUDO password:
…

Another way to accomplish privilege escalation is to create a user on the target machine, then grant the user passwordless sudo privileges to either all commands or a restricted list of commands.

Run sudo visudo and enter a line like the below:

%alice ALL= NOPASSWD: /usr/bin/service

The line means the user 'alice' does not enter a password when they run something like sudo service xxxx start.

Another way to accomplish privilege escalation is to create an Ansible vault:

ansible-vault create myvault

For more info see http://stackoverflow.com/questions/21870083/specify-sudo-password-for-ansible

Boto 3 - The AWS SDK for Python

Some Ansible modules use the python 2.x language and the Boto Amazon Web Services (AWS) Software Development Kit (SDK).

Boto documentation: http://boto3.readthedocs.io/en/latest/

To install boto typically:

$ pip install boto

If you get this kind of error:

fatal: [localhost]:
FAILED! => {
  "changed": false,
  "failed": true,
  "msg": "boto required for this module, install via pip or your package manager"
}

Then you need to tell Ansible how to find the python interpreter and the boto package.

To tell Ansible how to find the python interpreter, we prefer using the host file like this:

localhost ansible_python_interpreter="/usr/bin/env python"

Sidenote: to install boto3 globally to your system using python3, one way is to do is:

$ sudo su -
$ cd /opt
$ git clone https://github.com/boto/boto3
$ cd boto3
$ python3 setup.py install