Add docs/tech_docs/cloud-init.md

docs/tech_docs/cloud-init.md

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+Here's a simple example of using cloud-init to automate the configuration of an instance on first boot:
+
+```yaml
+#cloud-config
+
+# Update packages on first boot
+package_update: true
+package_upgrade: true
+
+# Install additional packages
+packages:
+  - nginx
+  - php-fpm
+
+# Write files to the system
+write_files:
+  - path: /var/www/html/index.php
+    content: |
+      <?php
+      phpinfo();
+      ?>
+
+# Run commands on first boot
+runcmd:
+  - systemctl start nginx
+  - systemctl enable nginx
+
+# Create a user
+users:
+  - name: webadmin
+    groups: sudo
+    shell: /bin/bash
+    sudo: ['ALL=(ALL) NOPASSWD:ALL']
+    ssh_authorized_keys:
+      - ssh-rsa AAAAB3NzaC1yc2EAA...your_public_ssh_key_here
+
+# Configure SSH access
+ssh_pwauth: false
+disable_root: true
+```
+
+In this example:
+
+1. The `package_update` and `package_upgrade` directives ensure that the system packages are updated on first boot.
+
+2. The `packages` section specifies additional packages to be installed, in this case, `nginx` and `php-fpm`.
+
+3. The `write_files` section is used to create a file on the system. Here, it creates a simple PHP script at `/var/www/html/index.php`.
+
+4. The `runcmd` section specifies commands to be executed on first boot. In this case, it starts and enables the Nginx service.
+
+5. The `users` section is used to create a user named `webadmin` with sudo privileges and an authorized SSH key.
+
+6. The `ssh_pwauth` and `disable_root` directives are used to configure SSH access, disabling password authentication and root login.
+
+To use this cloud-init configuration, you would save it as a YAML file (e.g., `cloud-config.yaml`) and provide it to your cloud provider or provisioning tool when launching a new instance.
+
+Cloud-init will execute the specified configuration on the instance's first boot, automating the process of updating packages, installing software, creating files and users, and configuring SSH access.
+
+This is just a simple example, but cloud-init supports a wide range of directives and modules for configuring various aspects of an instance, such as networking, storage, and more.