How to create deployment images used in virtualized environments

Overview #

You can quickly deploy WP Squared on Virtual Private Servers (VPS) or Virtual Machines (VM) using images created from a template system. Follow these simple steps to build and prepare an image, using the snapshot_prep script, so that every instance will be ready for use without manual setup.

Prepare your system for templating #

Prepare for templating by ensuring the following system requirements:

• Use 64-bit only: WP Squared works only on 64-bit systems.
• Disk size: Start with a virtual disk size of at least 20 GB. You can expand this later after deployment.

Pre-configure essential files (optional) #

Before you run the snapshot_prep script, configure the following files:

This pre-configuration eliminates the need to manually log into each VM to configure basic settings before customer access.

Security and system updates #

Before installing WP Squared, perform the following tasks:

• Update everything: Apply the latest OS and security patches.
• Clean up: Remove temporary files, logs, unique identifiers (like SSH keys and hostnames).
• Standardize: Make sure there’s nothing system-unique that could cause problems when you clone or start new VMs.

Install WP Squared #

After you finish preconfiguring your installation, you can install WP Squared. For more information, read our installation documentation.

Run the snapshot_prep script #

You can use the snapshot_prep script to prepare WP Squared servers for creating deployment images used in virtualized environments such as VPS or VM templates. The script cleans up server configurations and removes elements that could cause issues when cloning or deploying the image to new servers.

Basic usage #

You can run the snapshot_prep script from the command line with various options to control its behavior.

The basic command syntax:

/usr/local/cpanel/scripts/snapshot_prep

Options #

The snapshot_prep script provides the following options to customize its behavior:

For plugin developers – add custom tasks (optional) #

If you maintain third-party software for WP Squared servers, you can provide a plugin for your users to run with the snapshot_prep script. By using your plugin, users can run additional tasks when preparing their servers to create deployment images. For example, imagine your software includes a unique access token. You want each instance created from an image to have its own unique token. In this case, we recommend creating a third-party plugin that adds a task to perform the following:

• Clean the token when a user runs the snapshot_prep script so that the token is not included in the image.

• Generate a new token upon the first boot of instances created from the image.

For a description of these tasks, as well as all other tasks in this script, use the --list-tasks option.

The snapshot_prep script uses .json files to point to a third-party plugin script. Before a plugin can run, your software must install a .json file in the /var/cpanel/snapshot_prep.d directory on your user’s server.

The .json file must use the following format:

1{
2  "name": "exampleplugin",
3  "type": "non-repair only",
4  "pre": ["/var/cpanel/exampleplugin.py", "--before"],
5  "post": ["/var/cpanel/exampleplugin.py", "--after"],
6  "description": "Perform a task.\n"
7}

The .json file includes the following keys:

Dependencies for third-party plugins #

This system allows third-party plugins to customize or replace the default dependencies as needed. Third-party plugins in this system can define their own dependencies using the deps key in the plugin’s .json file.

By default, if no dependencies are specified, the following tasks are used as the default dependencies for all third-party plugins:

• ipaddr_and_hostname
• mysql
• cpwhm_misc

However, these defaults can be overridden by specifying a deps key in the plugin’s .json file. The deps key should contain a list of one or more tasks that must run before this plugin. For example:

1{
2  "name": "exampleplugin",
3  "type": "non-repair only",
4  "pre": ["/var/cpanel/exampleplugin.py", "--before"],
5  "post": ["/var/cpanel/exampleplugin.py", "--after"],
6  "description": "Perform a task.\n",
7  "deps": ["wp_toolkit"],
8  "before": ["wp2"]
9}

After running the script #

Once completed, the script destroys some configuration and user data. Make sure there are no failed tasks. A success message will appear: System is ready for snapshotting.

If you need to remove the saved config file copies before imaging, run the following command:

/usr/local/cpanel/scripts/snapshot_prep --delete-saved-copies

If successful, the system will display the following success message: Deleted saved copies of configuration files.

Final template configuration #

Your templates must meet or exceed our system requirements. Most providers offer a few different templates.

Deployment #

When deploying a new VPS/VM from your image, the system runs the post_snapshot script automatically to finish configuring the instance. If you used the --no-post-service option, run /usr/local/cpanel/scripts/post_snapshot script manually after the first boot. Consider using tools like libguestfs or virt-sysprep (--firstboot option) or your hypervisor’s similar features to run any further setup scripts. However, be cautious not to accidentally remove user accounts or cron jobs.