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10 Ansible modules you need to know
See examples and learn the most important modules for automating
everyday tasks with Ansible.
Ansible is an open source IT configuration management and automation platform. It uses human-readable YAML templates so users can program repetitive tasks to happen automatically without having to learn an advanced programming language.
Ansible is agentless, which means the nodes it manages do not require any software to be installed on them. This eliminates potential security vulnerabilities and makes overall management smoother.
Ansible modules are standalone scripts that can be used inside an Ansible playbook. A playbook consists of a play, and a play consists of tasks. These concepts may seem confusing if you're new to Ansible, but as you begin writing and working more with playbooks, they will become familiar.
There are some modules that are frequently used in automating everyday tasks; those are the ones that we will cover in this article.
Ansible has three main files that you need to consider:
- Host/inventory file: Contains the entry of the nodes that need to be managed
- Ansible.cfg file: Located by default at /etc/ansible/ansible.cfg, it has the necessary privilege escalation options and the location of the inventory file
- Main file: A playbook that has modules that perform various tasks on a host listed in an inventory or host file
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
Conclusion
There are tons of modules available in Ansible, but these ten are the most basic and powerful ones you can use for an automation job. As your requirements change, you can learn about other useful modules by entering ansible-doc <module-name> on the command line or refer to the official documentation.
via: https://opensource.com/article/19/9/must-know-ansible-modules
作者：DirectedSoul 选题：lujun9972 译者：译者ID 校对：校对者ID