Generate files from Jinja2 templates: a hosts file built from every node's facts, a hardware report with each host's own values, and a configuration file checked with validate before it's installed.

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) and node2 (10.99.1.12) are in the group webservers, node3 (10.99.1.13) in dbservers; all three are AlmaLinux 10 containers. Containers share the VM's memory and disks, so the lab gives each node its own memory size and disks, as Ansible's facts see them: they differ from node to node. For a root shell on a node, sudo podman exec -it node1 bash.

Tasks

Generate /etc/myhosts on the database servers from a template that lists every managed node, one line each, as ADDRESS FQDN SHORT-NAME, for example 10.99.1.11 node1.lab.example node1. The web servers get no /etc/myhosts.
Write a hardware report template and deploy it to /root/hwreport.txt on every node, with each node's own values, in this form:
```
HOST=node1
MEMORY=<memory in MiB>
BIOS=<BIOS version>
DISK_SIZE_VDB=<size of disk vdb>
DISK_SIZE_VDD=<size of disk vdd>
```
A missing disk shows as NONE.
Write /home/greg/ansible/sshd.yml, which templates the sshd drop-in /etc/ssh/sshd_config.d/50-lab.conf on all nodes with the line PermitRootLogin {{ sshd_root_login }} (the variable is no by default) and checks it with validate before installing it. Then try -e sshd_root_login=maybe: the task fails with "failed to validate", and the old file is unchanged.

Hints

hostvars[host]['ansible_facts'] has another host's facts, but only if the play gathered them: target all and limit the task with when.
ansible_facts['default_ipv4']['address'], ['fqdn'], ['hostname'].
ansible_facts['memtotal_mb'], ['bios_version'], and ansible_facts['devices']['vdb']['size'] | default('NONE').
validate: /usr/sbin/sshd -t -f %s.