Most important modules for automating everyday tasks with Ansible.

Fonte: https://opensource.com/article/19/9/must-know-ansible-modules , em 29-07-2020

Module 1: Package management

There is a module for most popular package managers, such as DNF and APT, to enable you to install any package on a system. Functionality depends entirely on the package manager, but usually these modules can install, upgrade, downgrade, remove, and list packages. The names of relevant modules are easy to guess. For example, the DNF module is dnf_module, the old YUM module (required for Python 2 compatibility) is yum_module, while the APT module is apt_module, the Slackpkg module is slackpkg_module, and so on.

Example 1:

- name: install the latest version of Apache and MariaDB
dnf:
name:
- httpd
- mariadb-server
state: latest

This installs the Apache web server and the MariaDB SQL database.

Example 2:

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

This installs the list of packages and helps download multiple packages.

Module 2: Service

After installing a package, you need a module to start it. The service module enables you to start, stop, and reload installed packages; this comes in pretty handy.

Example 1:

- name: Start service foo, based on running process /usr/bin/foo
service:
name: foo
pattern: /usr/bin/foo
state: started

This starts the service foo.

Example 2:

- name: Restart network service for interface eth0
service:
name: network
state: restarted
args: eth0

This restarts the network service of the interface eth0.

Module 3: Copy

The copy module copies a file from the local or remote machine to a location on the remote machine.

Example 1:

- name: Copy a new "ntp.conf file into place, backing up the original if it differs from the copied version
copy:
src: /mine/ntp.conf
dest: /etc/ntp.conf
owner: root
group: root
mode: '0644'
backup: yes

Example 2:

- name: Copy file with owner and permission, using symbolic representation
copy:
src: /srv/myfiles/foo.conf
dest: /etc/foo.conf
owner: foo
group: foo
mode: u=rw,g=r,o=r

Module 4: Debug

The debug module prints statements during execution and can be useful for debugging variables or expressions without having to halt the playbook.

Example 1:

- name: Display all variables/facts known for a host
debug:
var: hostvars[inventory_hostname]
verbosity: 4

This displays all the variable information for a host that is defined in the inventory file.

Example 2:

- name: Write some content in a file /tmp/foo.txt
copy:
dest: /tmp/foo.txt
content: |
Good Morning!
Awesome sunshine today.
register: display_file_content
- name: Debug display_file_content
debug:
var: display_file_content
verbosity: 2

This registers the content of the copy module output and displays it only when you specify verbosity as 2. For example:

ansible-playbook demo.yaml -vv

Module 5: File

The file module manages the file and its properties.

It sets attributes of files, symlinks, or directories.
It also removes files, symlinks, or directories.

Example 1:

- name: Change file ownership, group and permissions
file:
path: /etc/foo.conf
owner: foo
group: foo
mode: '0644'

This creates a file named foo.conf and sets the permission to 0644.

Example 2:

- name: Create a directory if it does not exist
file:
path: /etc/some_directory
state: directory
mode: '0755'

This creates a directory named some_directory and sets the permission to 0755.

Module 6: Lineinfile

The lineinfile module manages lines in a text file.

It ensures a particular line is in a file or replaces an existing line using a back-referenced regular expression.
It's primarily useful when you want to change just a single line in a file.

Example 1:

- name: Ensure SELinux is set to enforcing mode
lineinfile:
path: /etc/selinux/config
regexp: '^SELINUX='
line: SELINUX=enforcing

This sets the value of SELINUX=enforcing.

Example 2:

- name: Add a line to a file if the file does not exist, without passing regexp
lineinfile:
path: /etc/resolv.conf
line: 192.168.1.99 foo.lab.net foo
create: yes

This adds an entry for the IP and hostname in the resolv.conf file.

Module 7: Git

The git module manages git checkouts of repositories to deploy files or software.

Example 1:

# Example Create git archive from repo
- git:
repo: https://github.com/ansible/ansible-examples.git
dest: /src/ansible-examples
archive: /tmp/ansible-examples.zip

Example 2:

- git:
repo: https://github.com/ansible/ansible-examples.git
dest: /src/ansible-examples
separate_git_dir: /src/ansible-examples.git

This clones a repo with a separate Git directory.

Module 8: Cli_command

The cli_command module, first available in Ansible 2.7, provides a platform-agnostic way of pushing text-based configurations to network devices over the network_cli connection plugin.

Example 1:

- name: commit with comment
cli_config:
config: set system host-name foo
commit_comment: this is a test

This sets the hostname for a switch and exits with a commit message.

Example 2:

- name: configurable backup path
cli_config:
config: "{{ lookup('template', 'basic/config.j2') }}"
backup: yes
backup_options:
filename: backup.cfg
dir_path: /home/user

This backs up a config to a different destination file.

Module 9: Archive

The archive module creates a compressed archive of one or more files. By default, it assumes the compression source exists on the target.

Example 1:

- name: Compress directory /path/to/foo/ into /path/to/foo.tgz
archive:
path: /path/to/foo
dest: /path/to/foo.tgz

Example 2:

- name: Create a bz2 archive of multiple files, rooted at /path
archive:
path:
- /path/to/foo
- /path/wong/foo
dest: /path/file.tar.bz2
format: bz2

Module 10: Command

One of the most basic but useful modules, the command module takes the command name followed by a list of space-delimited arguments.

Example 1:

- name: return motd to registered var
command: cat /etc/motd
register: mymotd

Example 2:

- name: Change the working directory to somedir/ and run the command as db_owner if /path/to/database does not exist.
command: /usr/bin/make_database.sh db_user db_name
become: yes
become_user: db_owner
args:
chdir: somedir/
creates: /path/to/database