Validate a working configuration using ad hoc Ansible commands

In this article, you will learn how to run ad hoc commands with Ansible. Although YAML-based playbooks are the recommended method for automating tasks—enabling reusability, version control with Git, and easy sharing—ad hoc commands provide a quick and efficient alternative for testing modules, verifying connectivity, or gathering one-off information from multiple servers.

Using a YAML Playbook for Connectivity Testing

For administrators managing virtual machines, a simple playbook using the ping module is an excellent way to test connectivity. Below is an example playbook that pings all target servers:

---
- name: Ping Servers
  hosts: all
  tasks:
    - ping:

To run the playbook, execute the following command in your terminal:

ansible-playbook playbook.yml

Executing Ad-Hoc Commands Directly

If you prefer not to create a playbook, you can achieve the same result using an ad hoc command. Use the -m option to specify the module and designate the target hosts. The command below pings all servers:

ansible -m ping all

When executed, the output appears in JSON format for each host, similar to the following:

web2 | SUCCESS => {
    "changed": false,
    "ping": "pong"
}
web1 | SUCCESS => {
    "changed": false,
    "ping": "pong"
}

Running Arbitrary Commands

To run an arbitrary command on all hosts, use the -a option to pass the command directly. For instance, to display the contents of the /etc/hosts file, run:

ansible -a 'cat /etc/hosts' all

The output will be similar to this:

web1 | CHANGED | rc=0 >>
127.0.0.1 localhost
::1 localhost ip6-localhost ip6-loopback
fe00::0 ip6-localnet
ff00::0 ip6-mcastprefix
ff02::1 ip6-allnodes
ff02::2 ip6-allrouters
172.20.1.100 web1
web2 | CHANGED | rc=0 >>
127.0.0.1 localhost
::1 localhost ip6-localhost ip6-loopback
fe00::0 ip6-localnet
ff00::0 ip6-mcastprefix
ff02::1 ip6-allnodes
ff02::2 ip6-allrouters
172.20.1.100 web1

Privilege Escalation with Ad-Hoc Commands

You can also include privilege escalation options (such as become or become_user) with these ad hoc commands, just as you would when using a playbook. This flexibility makes ad hoc commands a powerful tool for managing your infrastructure on the fly.

Continue exploring additional methods to effectively utilize ad hoc commands in Ansible for efficient infrastructure management.