Ansible packages and service modules

Ansible packages and service modules In this post I would like to take you to the most important Linux administration tasks which can be used regularly in their daily activities that can be automated with Ansible. 

How do Linux Package Managers works?

Every Linux Operating system allow us to install any software using package managers such as yum, dnf, apt, deb or apk any other option. 

Here I've explored more details about this package mangers how they are working. If we take RedHat flavor Linux systems such as CentOS, SuSe, RHEL uses actually RPM as package manager. But the CLI clients are available such as yum(Yellowdog updater modified) and in the latest versions using improved yum that is dnf command utility which is known as "Dandified Yum". 

The service or systemctl commands

After installation we need to start, stop or restart or check status that service using systemctl or service command as per the System availability.

Ansible package manager modules connection with front-backend utilities

 
First we will experiment with package managers dnf usage in Ansible. We can target simple two playbooks where you should have inventory groups defined for webserver, database.

Prerequisite:

The inventory file content with the webserver and database groups as following

[ansible@master qa]$ cat hostqa.yml

all:
  children:
    qa:
      children:
        qawebserver:
          hosts:
            node[1:2]-vt:
        qadbserver:
          hosts:
            node3-vt:
        qalb:
          hosts:
            node4-vt:

How to install packages using ansible yum module?

The Ansible yum module is allow us to install the packages on the target hosts. where you can tell the action using state.

---
# File: nginx_yum_installation.yml

- name: install and start nginx
  hosts: "{{ targets | default ('webserver') }}"
  become: yes
  tasks:
    - name: install nginx
      yum:
        name: nginx
        state: present
        update_cache: true

    - name: start nginx
      service:
        name: nginx
        state: started

  

The execution of the above playbook output as:

ansible-playbook nginx_yum_installation.yml
  

Ansible yum module for install nginx and start the service

How to uninstall package using ansible yum module?

The following ansible playbook code will stop the service and remove the package from the target box.

  ---
# Filename: nginx_stop_yumremove.yml
- name: stop and remove nginx
  hosts: "{{ targets | default('localhost') }}"
  become: yes
  gather_facts: no
  tasks:
    - name: stop nginx server
      service:
        name: nginx
        state: stopped

    - name: remove nginix
      yum:
        name: nginx
        state: absent

  

Execution outcome

   ansible-playbook -e targets=qawebserver nginx_stop_yumremove.yml --check
   ansible-playbook -e targets=qawebserver nginx_stop_yumremove.yml 
  

Ansible yum module to remove nginx package

How to install packages using ansible apt module?

The Ansible apt module is allow us to install the packages on the target hosts. where you can tell the action using state.

  ---
# Filename: nginx_apt_installation.yml

- name: install and start nginx
  hosts: "{{ targets | default ('loadbalancer') }}"
  become: yes
  tasks:
    - name: install nginx
      apt:
        name: nginx
        state: present
        update_cache: false

    - name: start nginx
      service:
        name: nginx
        state: started
  

The execution of the above playbook output as:

ansible-playbook nginx_apt_installation.yml
  

How to install a package with ansible dnf module?

If you are working on CentOs8 or Oracle Linux 8 or RHEL 8 then you can use dnf module. The web group target to install nginx webserver, and database target to install with mysql database.

---
- hosts: webserver
  tasks:
    - name: install nginx
      dnf: name=nginx state=present update_cache=true
  

Package manager module can be executed on the target machine with ansible user generally, but it requires sudo access so we need to use become parameter value as 'yes'. In adhoc command execution we can use -b or --become option.

ansible webserver -m yum -a "name=httpd state=latest" -b

How to list out the package is installed?

The yum module can be used to determine if a package is available and installed on the managed node (e.g. the target VM). This ansible module execution is similar to the `yum info` command in CLI. Let's examine "nginx" installed on the web boxes with the followng playbook.

- name: List out the yum installed packages
  hosts: "{{ targets | default ('loadbalancer') }}"
  gather_facts: false
  #remote_user: root
  become: yes
  tasks:
    - name: determine if a package is installed
      yum:
        list: "{{ package }}"
      register: out

    - debug:
        msg:
          - "package: {{ package }}"
          - "yumstate: {{ out.results[0].yumstate }}"
          - "yumstate: {{ out.results[1].yumstate }}"
          - "version: {{ out.results[1].version }}"

		

Executed with the following command :

ansible-playbook -e targets=node1-vt -e package=nginx yum_list.yml

The screen screen will look like this:

Ansible yum module listing out about a package

  To check already httpd is installed on a machine:

rpm -qa|grep httpd 

Important Note:

The name very first you defined used hyphen, here hyphen is only used when you want general information for the playbook reader to indicate about the task. when we use module attribute with name should not with hyphen.

References Ansible documentation:

1. Package manger - dnf  

2. Package manager - apt  

3. Package manager - yum 

4. default target in ansible