Ansible - Things That Can Done

This article is basically a guide on using Ansible.

1. Obtain a Environment Variable – To retrieve a Environment variable we can use

- name: Copy JAVA_HOME location to variable

  command:  bash -c -l "echo $JAVA_HOME"

  register: java_loc

- name: show debug                         

  debug: var=java_loc 

2. Retrieve executables – In order to retrieve executables available in remote machine. Ex- to get where bash resides we can use

 - name: Where is Bash

   command: bash -c -l "which bash"

   register: whereis_bash

 - name: show Bash

   debug: var=whereis_bash

3. Wait for Port – When ever we run a script and wait for particular port to start we can use

- name: Wait for the nexus-iq Port to start

   wait_for: port=8070 delay=60

4. Template Variables – When ever we want to pass variables to template we can use

 - name: copy nexus-iq.sh start script

   template:

     src: nexus-iq.j2

     dest: "{{nexus_iq_dir}}/nexus-iq.sh"

     mode: "0755"

   vars:

     java_path: "{{java_loc.stdout}}"

     nexus_iq_path: "{{nexus_deploy_location}}"

     bash_is: "{{whereis_bash.stdout}}"

5. Update environment variables – We use source command to update environment variables .this can be done in Ansible as

- name: Source Bashrc to Update Env Variables

  shell: source {{ installation_user_home }}/.bashrc

6. Replace – There are some cases where we might need to replace things in the obtained values from remote hosts. We can do that in anisble as,

- name: Copy the jetty-https Template to the Remote Machine

    template:

       src: jetty-https.j2

       dest: "{{nexus_dir}}/nexus-{{nexus_version}}/conf/jetty-https.xml"

       mode: "0644"

       backup: "yes"

    vars:

      OBF: "{{ generated_password.stdout | replace('\n', '') | replace('^M', '') }}"

7. Pipelining - pipelining reduces the number of ssh connections required to execute a module on the remote server, by piping scripts to the ssh session instead of copying it.

This results in the performance improvement.

Note - pipe ling will only work if the option requiretty is disabled on all remote machines in the sudoers file

[ssh_connection]

pipelining = True

8. Turn off Facts -if you are not using any facts in your playbook ,we can disable that using the

- hosts: dev

gather_facts: False

9. Step by Step Task - an ansible playbook will run all the tasks in a sequential way. What if we want to check before running the task. --step in Ansible will let you decide which tasks you want to run

ansible-playbook sample.yml –step

10. Dry Run – Some time we want our Ansible scripts to run but with out making any changes. This is something like testing our Scripts. We can do this as

ansible-playbook playbook.yml –check

11. Pause a Playbook – In Some cases we want out playbook to pause until some other action on the remote machine is done. We can do this by adding,

pause: prompt="waiting 60 Seconds" minutes=1 seconds=30

12. List Tasks – There may be cases where we want to check the tasks available before running them. This can done by

[root@vx111a delegate]# ansible-playbook --list-tasks sample-playbook.yml

playbook: sample-playbook.yml

  play #1 (cent):      TAGS: []

    Install zenity        TAGS: []

    configure zenity    TAGS: []

    Tell Master TAGS: []

13. Syntax Checking – In order to check the syntax of the playbook we can use

[root@vx111a delegate]# ansible-playbook --syntax-check sample-playbook.yml

14. Verbose Mode – Run Ansible playbook in verbose mode as,

[root@vx111a delegate]# ansible-playbook --verbose sample-playbook.yml

15. Delegate – There are some cases where we want our actions to be delegated to other machines. To “delegate” tasks to the control machine, or any other host that the control machine can SSH to we can do

    - name: Tell Master

      action: shell echo "{{ansible_fqdn}} done" >> /tmp/list

      delegate_to: 172.16.202.97

In the above snippet we are delegating our task to 172.16.202.97 Machine

16. Send Mail – There are cases where we need to send mail based on Our actions. We can do this in Ansible using

  - name: Send Mail Alert

      local_action: mail

                    host="127.0.0.1"

                    subject="[Ansible] Testing Mail"

                    body="Hello the Play book ran successfully"

                    to="XXX@gmail.com"

                    from="root" 

More to Come. I will be adding more of the use cases in Ansible.

Happy learning J