Learning Through the Web: Ansible

This list is a companion to my article Learning Through the Web: Lessons Learned

As mentioned in the article, during the learning period I get through, I try to read a relevant book and spot the things I missed on the web. This list is exactly this for ansible. The book read is Ansible Up and Running [1]

  • Firstly something that comes handy, you can make your Ansible playbooks executable
  • using shebang by adding #! /usr/bin/env ansible-playbook at the beginning of the file
  • It is a good practice to keep files and jinja templates on separate directories (/files, /templates)
  • because during the execution of each respective task, (file or template)
  • ansible will check those directories first, either it is in a role or simply a playbook
  • Handlers in ansible run only on changed task status, not always
  • default/main.yml variables are meant to be overridden whereas vars/main.yml are not
  • You can define dependencies between roles
  • You can pass roles variables using the following syntax
    roles:
    - { role: ntp, ntp_server=ntp.ubuntu.com }
  • Ansible uses ssh connections, it uses 2 ssh connections per task,
  • one to copy the file on the host a second one to execute it
  • You can reduce the number of ssh connections, hence the required execution time,
  • using pipelining, use one connection to copy and execute the script
  • You can further reduce the execution time by reducing the number of TCP connections
  • using ssh multiplexing, which will use the same TCP connection to pass all the ssh
  • connections through it
  • Ansible gathers metadata about each host, those metadata in ansible terms are called facts.
  • You can further reduce the execution time by enabling facts caching
  • Ansible import is a pseudo import, it will copy all the reference in the file and it will make
  • an uber file that will contain everything, pretty much as c does

 

References 

[1] Ansible: Up and Running: Automating Configuration Management and Deployment the Easy Way, Lorin Hochstein

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