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Oracle® VM Template Builder Installation and User's Guide Release 2.1 Part Number E14391-01 |
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# 1 Overview of Oracle VM Template Builder

This Chapter contains an overview of Oracle VM Template Builder. This Chapter contains:

- Overview

- Oracle VM Templates Concepts

- Designing Templates

## 1.1 Overview

The use of Oracle VM templates for the deployment of applications in Oracle VM guest virtual machines eliminates the need for a user to install and configure the operating system or applications. The templates can simply be downloaded and the guest virtual machines started either from the Oracle VM Manager browser-based interface, or by using an xm command issued at the Oracle VM Server command-line.

Oracle VM Template Builder facilitates the development of Oracle VM templates. It is a kit that includes a web-based application, and a minimum set of the packages for supported guest virtual machine operating systems. Oracle VM Template Builder is itself distributed as a template, and as an RPM.

Installation and configuration of applications and the operating system is eliminated. Creating guest virtual machine templates for your entire stack of applications, operating system and hardware reduces the deployment time for guest virtual machines.

The operating system and applications are configured when the template is started (booted). The configuration can be done based on certain default values and actions, or dynamically based on the user's input. For example, to include a static IP address in a guest virtual machine, you can prompt the user for an IP address, gateway, DNS server, and netmask. These values are then added to the guest virtual machine. The nondefault settings which require user input are created during development of the template.

## 1.2 Oracle VM Templates Concepts

A template is a snapshot of a preconfigured virtual machine. To create this snapshot Oracle VM Template Builder:

- Creates the virtual machine with the desired operating system

- Installs and configures the target software

- If required, implements the dynamic (initial boot-time) configuration for the operating system and software

The virtual machine with the desired operating system is created from scratch. Oracle VM Template Builder builds the template for you, removing the need to perform these steps manually.

Oracle VM Template Builder uses “Just enough OS” or “JeOS” to facilitate building an operating system instance with only the absolute minimum packages you need for your template. This helps reduce the disk footprint by up to 2GB or more per guest virtual machine. It also improves security and reliability of the guest virtual machine. You can add further packages to customize your guest virtual machine.

Dynamic boot time configuration actions can be implemented in scripts. The images created with Oracle VM Template Builder include an RPM, named ovm-template-config.rpm, which performs operating system configuration. The ovm-template-config RPM can also run your own template scripts to configure the application software installed in the template. See Chapter 7, "Creating Template Scripts" for information on creating template scripts.

A template created with Oracle VM Template Builder contains one guest virtual machine, and consists of one or more binary files, and a text file. The binary files are the disk images of the guest virtual machine. The text file is a virtual machine configuration file (vm.cfg). Oracle VM Template Builder creates a single file archive of these files as a .tar.gz file. A template created with Oracle VM Template Builder may only contain one guest virtual machine. For example, a template might contain:

    oracle11g
              /system.img      (disk image with operating system)
              /oracle11g.img   (disk image with Oracle software)
              /vm.cfg          (guest configuration file)

Future releases of Oracle VM Template Builder may allow you to create templates with multiple guest virtual machines.

## 1.3 Designing Templates

A template may support many different use cases, customer requirements, and topologies, or it may be specific to a certain need. The template, when deployed, may be required to support standard application and operating system procedures going forward, for example:

- Patch updates

- Upgrades

- Configuration

- Technical support access

You should consider the requirements of the template before you begin. For example:

- Operating system type, and version

- Paravirtualized or hardware virtualized guest

- Software applications

- Software configuration

- Software installation directory

- Software installation partition size

- Number of virtual CPUs

- Virtual memory size

- Disk swap size

- Root partition size after operating system is installed

- Disk image mount point(s)

- Template name (the default name for the archive and the guest virtual machine)

- Anything specific for your software applications or operating system, for example a database repository

To maximize the performance of guest virtual machines, Oracle recommends you create paravirtualized guest virtual machines in templates.