Understanding Ad-hoc commands in Ansible

Ansible ad hoc commands are one-liners designed to achieve a very specific task they are like quick snippets and your compact Swiss army knife when you want to do a quick task across multiple machines.

To put simply, Ansible ad hoc commands are one-liner Linux shell commands and playbooks are like a shell script, a collective of many commands with logic.

Ansible ad hoc commands come in handy when you want to perform a quick task.

Ansible ad hoc ping command to ping 3 servers from the inventory file

Ansible ad hoc command to ping a host:

ansible -i /path/to/inventory/file server1:server2:server3 -m ping

This command uses the ansible command with the following options:

• -i /path/to/inventory/file: specifies the path to the inventory file containing the servers we want to ping. /etc/ansible/hosts are by default paths of the inventory file. there is no need to write a path in the ansible ad hoc command. If your inventory file is at a different location then you need to write the path of the inventory file in ad hoc command.

• server1:server2:server3: specifies the list of servers to ping, separated by colons.

• -m ping: specifies that we want to use the ping module to ping the servers.

• In my case I have added the naming convention as Ansible-Server1 in the /etc/ansible/hosts file, that is why I used the command as shown below

    ansible Server1:Server2 -m ping
  

  

Write an ansible ad hoc command to check uptime

ansible -i /path/to/inventory/file all -m command -a uptime

This command uses the ansible command with the following options:

• -m command: specifies that we want to use the command module to execute the uptime command on the remote servers.

• -a uptime: specifies the arguments to pass to the command module, which in this case is simply the uptime command.

    ansible all -m command -a uptime
  

  

Ansible ad hoc command to check the free memory or memory usage of hosts

 ansible -i /path/to/inventory/file all -a "free -m"

-a "free -m": the -a option specifies the arguments to pass to the command to be executed on the remote hosts. In this case, the free -m command is executed to show the memory usage on each host.

ad-hoc command to get physical memory allocated to the host

ansible all -m shell -a "cat /proc/meminfo|head -2"

• -m shell: the -m option specifies the module to use to execute the command on the remote hosts. In this case, the shell module is used to execute the command.

• -a "cat /proc/meminfo|head -2": the -a option specifies the arguments to pass to the module to execute the command on the remote hosts. In this case, the cat /proc/meminfo|head -2 command is executed to display the first two lines of the /proc/meminfo file on each host.

  

To check the disk space on all hosts in an inventory file

ansible -i inventory_file all -m shell -a 'df -h'

This command uses the df command to show the disk space usage on each host in the inventory file.

The -m shell option is used to execute the command on the remote hosts using the shell.