Basic Syntax of Ansible Ad-Hoc Commands

Ansible ad-hoc commands allow you to perform quick, one-time tasks across multiple systems using a single command. Understanding the basic syntax is essential for using Ansible efficiently.

General Command Structure

The general structure of an Ansible ad-hoc command is:

ansible <host-pattern> -m <module> -a "<arguments>"

• ansible: the command-line tool for running ad-hoc tasks;
• <host-pattern>: specifies the group of hosts or individual host(s) to target, such as all to target every host in your inventory;
• -m <module>: selects the Ansible module to use, such as ping, shell, or yum;
• -a "<arguments>": provides arguments required by the chosen module; this part is optional, depending on the module.

Example: Checking Connectivity

To check the connection to all managed hosts, use the following command:

ansible all -m ping

• all: targets every host defined in your inventory file;
• -m ping: uses the ping module, which tests connectivity by attempting to run a simple Python command on each host.

When you run this command, you will see output indicating whether each host is reachable. This is a common first step to verify that your Ansible setup is working correctly.

Additional Options

You can also specify other options, such as:

• -u <username>: runs the command as a specific user;
• --become: escalates privileges (similar to sudo).

For instance, to run the ping module as the admin user with elevated privileges:

ansible all -m ping -u admin --become

These options help you adapt ad-hoc commands to different environments and requirements.

Managing Files

Create a file on remote servers using the file module:

ansible webservers -m file -a "path=/tmp/ansible-demo state=touch"

• This creates an empty file named ansible-demo in the /tmp directory on every host in the webservers group;
• The state=touch argument ensures the file exists (creating it if necessary).

Installing Packages

Install the httpd web server package on all web servers:

ansible webservers -m yum -a "name=httpd state=present"

• This uses the yum module to install the httpd package;
• The state=present argument ensures the package is installed.

Restarting Services

Restart the httpd service after installation:

ansible webservers -m service -a "name=httpd state=restarted"

• The service module manages services on remote hosts;
• This command restarts the httpd service on all hosts in the webservers group.

These examples show how ad-hoc commands let you quickly automate routine tasks across your infrastructure, saving time and reducing manual errors.

By breaking down each part of the command, you can adapt ad-hoc commands for different tasks and hosts as your automation needs grow.