linuxexpert-practice-labs/labs/ex294/8-1-creating-roles/README.md

EX294 8.1: Creating roles

Write a role that sets up a web server, give it a default that one host overrides, and include it only on hosts with enough memory.

Before you start

This VM is the control node. The lab creates the user greg (password Lab-Pass-1) and installs ansible-core. Work as greg, in /home/greg/ansible: its ansible.cfg reads the inventory inventory, logs in to the nodes as devops with greg's SSH key, and becomes root.

The managed nodes node1 (10.99.1.11), node2 (10.99.1.12) and node3 (10.99.1.13) are AlmaLinux 10 containers in the group webservers, with no web server and no firewall yet. Containers share the VM's memory, so the lab gives each its own as Ansible's facts see it: node1 and node2 have 4096 MiB, node3 has 1024 MiB. For a root shell on a node, sudo podman exec -it node1 bash.

Tasks

1. Create a role apache in /home/greg/ansible/roles/apache that installs httpd, starts and enables it, installs, starts and enables firewalld and opens the web port, and deploys a home page from a template showing the host's FQDN and IP address. Use it from a playbook on the web servers. curl http://node1/ and curl http://node2/ each show their own name and address (once task 2 moves node2 to port 8080, its page is at http://node2:8080/).
2. Give the role a default port of 80 in defaults/main.yml, and override it for node2 with 8080. node2 then answers on port 8080; node1 still uses 80 only.
3. Make the playbook include the role only on hosts with at least 2 GiB of memory, with include_role and a when, so node3 is skipped. If an earlier run put httpd on node3, remove it there.

Hints

• ansible-galaxy role init roles/apache makes the layout.
• ansible_facts['fqdn'] and ansible_facts['default_ipv4']['address'] in templates/index.html.j2.
• httpd already listens on 80; a template in /etc/httpd/conf.d/ can add Listen {{ apache_port }} when the port isn't 80, with a handler to restart httpd.
• ansible.posix.firewalld needs ansible-galaxy collection install ansible.posix; permanent: true and immediate: true.
• host_vars/node2.yml overrides a role default for one host.
• ansible.builtin.include_role is a task, so it takes when.