Exercise 2.2 - Inventories, credentials and ad hoc commands

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Create an Inventory

Let’s get started with: The first thing we need is an inventory of your managed hosts. This is the equivalent of an inventory file in Ansible Engine. There is a lot more to it (like dynamic inventories) but let’s start with the basics.

Create the inventory:

Parameter Value
NAME Workshop Inventory

Now there will be two inventories, the Demo Inventory and the Workshop Inventory. In the Workshop Inventory click the Hosts button, it will be empty since we have not added any hosts there.

So let’s add some hosts. First we need to have the list of all hosts which are accessible to you within this lab. These can be found in an inventory on the ansible control node on which Tower is installed. You’ll find the password for the SSH connection there as well.

Login to your Tower control host via SSH:


Replace workshopname by the workshop name provided to you, and the X in studentX by the student number provided to you.

ssh student<X>@student<X>.workshopname.rhdemo.io

You can find the inventory information at ~/lab_inventory/hosts. Output them with cat, they should look like:

$ cat ~/lab_inventory/hosts

node1 ansible_host=
node2 ansible_host=
node3 ansible_host=

ansible-1 ansible_host=


In your inventory the IP addresses will be different.

Note the names for the nodes and the IP addresses, we will use them to fill the inventory in Tower now:

You have now created an inventory with three managed hosts.

Machine Credentials

One of the great features of Ansible Tower is to make credentials usable to users without making them visible. To allow Tower to execute jobs on remote hosts, you must configure connection credentials.


This is one of the most important features of Tower: Credential Separation! Credentials are defined separately and not with the hosts or inventory settings.

As this is an important part of your Tower setup, why not make sure that connecting to the managed nodes from Tower is working?

To access the Tower host via SSH do the following:

[student<X>@ansible-1 ~]$ ssh student<X>@
student<X>@'s password:
Last login: Thu Jul  4 14:47:04 2019 from
[student<X>@node1 ~]$ sudo -i
[root@node1 ~]#

What does this mean?

Configure Machine Credentials

Now we will configure the credentials to access our managed hosts from Tower. In the RESOURCES menu choose Credentials. Now:

Click the plus button to add new credentials


Whenever you see a magnifiying glass icon next to an input field, clicking it will open a list to choose from.

You have now setup credentials to use later for your inventory hosts.

Run Ad Hoc Commands

As you’ve probably done with Ansible before you can run ad hoc commands from Tower as well.

The simple ping module doesn’t need options. For other modules you need to supply the command to run as an argument. Try the command module to find the userid of the executing user using an ad hoc command.


After choosing the module to run, Tower will provide a link to the docs page for the module when clicking the question mark next to “Arguments”. This is handy, give it a try.

How about trying to get some secret information from the system? Try to print out /etc/shadow.


Expect an error!

Oops, the last one didn’t went well, all red.

Re-run the last ad hoc command but this time tick the ENABLE PRIVILEGE ESCALATION box.

As you see, this time it worked. For tasks that have to run as root you need to escalate the privileges. This is the same as the become: yes you’ve probably used often in your Ansible Playbooks.

Challenge Lab: Ad Hoc Commands

Okay, a small challenge: Run an ad hoc to make sure the package “tmux” is installed on all hosts. If unsure, consult the documentation either via the web UI as shown above or by running [ansible@tower ~]$ ansible-doc yum on your Tower control host.


Solution below!


The yellow output of the command indicates Ansible has actually done something (here it needed to install the package). If you run the ad hoc command a second time, the output will be green and inform you that the package was already installed. So yellow in Ansible doesn’t mean “be careful”…​ ;-).

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