Chapter 3: Implementing an Ansible Playbook

Exercise: Building an inventory

You will build a static inventory for four web servers, grouping them three different ways (by city, by environment, and by country), then prove the groups are right with ansible-navigator inventory.

These are the four managed hosts and their properties:

Host name	Purpose	Location	Environment
`servera.lab.example.com`	Web server	Raleigh	Development
`serverb.lab.example.com`	Web server	Raleigh	Testing
`serverc.lab.example.com`	Web server	Mountain View	Production
`serverd.lab.example.com`	Web server	London	Production

The US cities (Raleigh and Mountain View) must also be children of a us group, so all US hosts can be managed together.

Building an Ansible inventory

Create a custom static inventory with groups and child groups.
Verify hosts and groups with ansible-navigator inventory.

Prerequisites: Complete control-node setup and the preceding lessons in this chapter. Run commands as student on workstation unless a step names another machine.

From the project directory, run the relevant home-lab check. For an exercise with several checkpoints, grade each state before changing or removing it:

lab grade playbook-inventory

The grader reads project files and host state. A passing report covers the listed checks; also perform the task’s independent connection, repeat-run, and reboot checks where requested.

Add a fifth host in London for testing. Predict which city, country, environment, and function selections change.

Record the published result first. The grader checks the original requirements, so a changed name or value may intentionally fail those checks.

An operations team needs to target these four servers by function, city, environment, and country.

Save a static inventory matching the host table above, using lowercase group names: webservers, raleigh, mountainview, london, development, testing, and production.
us must contain the Raleigh and Mountain View groups. Every host must belong to a named group.
Prove the complete host list, the production membership, and the inherited membership of us. No server configuration should change.

Move into the project directory

[student@workstation ~]$ cd ~/playbook-inventory
[student@workstation playbook-inventory]$

Write the inventory file

Create a file called inventory in the project directory. Try it yourself from the table above first, then compare with the solution.

[webservers]
server[a:d].lab.example.com

[raleigh]
servera.lab.example.com
serverb.lab.example.com

[mountainview]
serverc.lab.example.com

[london]
serverd.lab.example.com

[development]
servera.lab.example.com

[testing]
serverb.lab.example.com

[production]
serverc.lab.example.com
serverd.lab.example.com

[us:children]
raleigh
mountainview

Notice the alphabetic range server[a:d] for the webservers group.

List every host and group

Because this inventory is not the default, every command needs -i inventory.

[student@workstation playbook-inventory]$ ansible-navigator inventory \
> -i inventory -m stdout --list

In the JSON, check that all.children lists development, london, mountainview, production, raleigh, testing, ungrouped, us and webservers, and that us has mountainview and raleigh as children.

Confirm nothing is ungrouped

[student@workstation playbook-inventory]$ ansible-navigator inventory \
> -i inventory -m stdout --graph ungrouped
@ungrouped:

An empty group is the right answer: every host belongs to at least one named group.

Graph the environment groups

[student@workstation playbook-inventory]$ ansible-navigator inventory \
> -i inventory -m stdout --graph development
@development:
  |--servera.lab.example.com
[student@workstation playbook-inventory]$ ansible-navigator inventory \
> -i inventory -m stdout --graph testing
@testing:
  |--serverb.lab.example.com
[student@workstation playbook-inventory]$ ansible-navigator inventory \
> -i inventory -m stdout --graph production
@production:
  |--serverc.lab.example.com
  |--serverd.lab.example.com

Graph the nested us group

[student@workstation playbook-inventory]$ ansible-navigator inventory \
> -i inventory -m stdout --graph us
@us:
  |--@mountainview:
  |  |--serverc.lab.example.com
  |--@raleigh:
  |  |--servera.lab.example.com
  |  |--serverb.lab.example.com

Child groups are shown with an @ and their hosts are indented beneath them.

Browse it interactively

Run the command without -m stdout. Type :0 to browse groups, :1 to browse hosts, and :q to quit.

[student@workstation playbook-inventory]$ ansible-navigator inventory -i inventory
  Title              Description
0│Browse groups      Explore each inventory group and group members members
1│Browse hosts       Explore the inventory with a list of all hosts

Finish

Check your work with lab grade playbook-inventory, then put the exercise away with lab finish playbook-inventory.