YAML syntax

[Trevor]

Hello all,

After running the command "ansible-doc yum", toward the end of the output, there are some nice example snippets regarding the use of the "yum" module in a playbook.

One of the examples is the following:

- name: Download the nginx package but do not install it
  yum:
      name:
          - nginx
      state: latest 

What's prompting a question from me is the "nginx" package name being shown as a list item (- nginx).  Is there any functional difference between the package name being
shown in the form of:

       name:  nginx

versus 

       name:   
            -  nginx

If so, what do I gain by showing the package name as a list item?   Another example
in that same output (ansible-doc  yum) is the following:

- name: Install a list of packages
  yum:
      name:
           - nginx
           - postgresql
           - postgresql-server
      state: present

I can connect with that example,  There are three packages to be operated on, and it makes sense (to me) to use a "list".  

Okay, a little help here.

Hope everyone is safe and well!!!

[Alexandre · Accepted solution]

Hi

No problem to use one line form here:

- name: Install a list of packages
  yum:
    name: [nginx,postgresql,postgresql-server]
    state: present

[Trevor]

Thanks Alexandre for your reply.  Your information has advanced my understanding of YAML because I was not aware of the form that you provided.  Thank you for that.

I'm still not clear if there is something different in the funtionality of:

name:  nginx

      versus 

 name:   
     -  nginx  

Again, thank you advancing my YAML knowledge.

[Metsie · Accepted solution]

Hi Trevor,

AFAIK, there should not be any significant difference. The yum module supports both a string and a list. So you can choose to use the short syntax you provided here with no problems at all.

It is not recommended however to loop the yum module.

- name: install packages
  yum:
    name: "{{ item }}"
    state: latest
  loop:
    - nginx
    - postgresql
    - postgresql-server

Would run the yum module once for each package in the list (so three times in this example), where

- name: Install packages
  yum:
    name:
      - nginx
      - postgresql
      - postgresql-server
    state: latest

Would run the yum module a single time to install all packages at once.

[Trevor]

Hello Metsie,

Many thanks for your response to my query, and for the
additional information as well.

Hope you're safe and well!!!

Trevor