Ansible

• There is a master machine (where the command is dispatched, where ansible is installed and will orchestrate the commands) and a set of workers machines (where the commands must ran)

Install

• from http://docs.ansible.com/ansible/latest/installation_guide/intro_installation.html#latest-releases-via-apt-debian

Install ansible in the master machine

• From Debian_backports

su -c "apt-get -t stretch-backports install ansible"

OR

• From Ubuntu repository (old, failsafe)

su -
apt-get install dirmngr
apt-key adv --keyserver keyserver.ubuntu.com --recv-keys 93C4A3FD7BB9C367
add-apt-repository "deb http://ppa.launchpad.net/ansible/ansible/ubuntu trusty main"
etckeeper commit
apt-get update
apt-get install ansible
# test
ansible --version
exit

Config

• The follow is a simple config that configure a master and a worker machine. Note that:

1. sshd must be installed and running in each worker machine
2. ansible must be installed in the master machine, using the commands above

• configure ansible /etc/ansible/hosts file, specifying the hostname and ports of each worker (in this example we will configure 2 workers that are the same local machine, 'localhost' and '127.0.0.1', using default ssh port '22')

# the follow line just add 'localhost:22' line at the end of the config file
su -
echo 'localhost:22' >> /etc/ansible/hosts
echo '127.0.0.1:22' >> /etc/ansible/hosts
exit

• enable the ssh access to each worker, adding the public key of the user that will start the command

# in this case, the local pub key is added in the same machine user list of authorized keys
cat ~/.ssh/id_rsa.pub >> ~/.ssh/authorized_keys
# in a multi-machine real environment, the public key must be added in the host as well as in each worker

Run

• From the host machine, the user that has the public key configured can run a set of commands defined in a playbook file, this is an example of such file, filename.yaml:

---
- hosts: all
  become: False
  tasks:
    - name: show the hostname
      shell: hostname
    - name: show the current folder contents 
      shell: ls

The file specify a list item (each list item starts with a '-') to configure the workers where run (in this case, all hosts in /etc/ansible/hosts), does not requires root privileges defining 'become: False', and finally define the tasks as a list with two items, one that run the command 'hostname' and one that run the 'ls' command

• The previous file can be submitted with the follow command:

ansible-playbook -v filename.yaml

• The output is like the follows:

Using /etc/ansible/ansible.cfg as config file
 [WARNING]: A duplicate localhost-like entry was found (127.0.0.1). First found localhost was
localhost


PLAY [all] ***************************************************************************************

TASK [Gathering Facts] ***************************************************************************
ok: [127.0.0.1]
ok: [localhost]

TASK [show the hostname] *************************************************************************
changed: [127.0.0.1] => {"changed": true, "cmd": "hostname", "delta": "0:00:00.001861", "end": "2018-05-18 17:10:06.269964", "rc": 0, "start": "2018-05-18 17:10:06.268103", "stderr": "", "stderr_lines": [], "stdout": "YOURHOSTNAME", "stdout_lines": ["YOURHOSTNAME"]}
changed: [localhost] => {"changed": true, "cmd": "hostname", "delta": "0:00:00.001636", "end": "2018-05-18 17:10:06.270706", "rc": 0, "start": "2018-05-18 17:10:06.269070", "stderr": "", "stderr_lines": [], "stdout": "YOURHOSTNAME", "stdout_lines": ["YOURHOSTNAME"]}

TASK [show the current folder contents] **********************************************************
changed: [localhost] => {"changed": true, "cmd": "ls", "delta": "0:00:00.002065", "end": "2018-05-18 17:10:06.466266", "rc": 0, "start": "2018-05-18 17:10:06.464201", "stderr": "", "stderr_lines": [], "stdout": "FILE_1\nFILE_2\nFILE_...\nFILE_N", "stdout_lines": ["FILE_1", "FILE_2", "FILE_...", "FILE_N"]}
changed: [127.0.0.1] => {"changed": true, "cmd": "ls", "delta": "0:00:00.001849", "end": "2018-05-18 17:10:06.476125", "rc": 0, "start": "2018-05-18 17:10:06.474276", "stderr": "", "stderr_lines": [], "stdout": "FILE_1\nFILE_2\nFILE_...\nFILE_N", "stdout_lines": ["FILE_1", "FILE_2", "FILE_...", "FILE_N"]}

PLAY RECAP ***************************************************************************************
127.0.0.1                  : ok=3    changed=2    unreachable=0    failed=0   
localhost                  : ok=3    changed=2    unreachable=0    failed=0