EZ Templates Basics

All OS and application EZ templates are defined by the following features:

• EZ templates do not carry the necessary package files inside themselves. They contain only the information about what packages should be installed on the host to make the templates fully operational and from what network repository these packages should be downloaded.

  Note: For the sake of brevity, we will be saying throughout this guide that packages are included in EZ templates, which actually means that EZ templates contain the information on the corresponding packages without carrying the packages themselves.

• The dependencies of software packages included in an EZ template are automatically resolved during the packages installation on the host. So, if the specified packages require other packages to be installed, these packages are also downloaded from the repository and installed on the server. In case a package has requirements that conflict with existing software on the server or any dependencies for the package being installed cannot be satisfied, the package installation process fails without making any changes to the system.
• The EZ templates technology allows you to use the original OS and application vendor's packages and to receive the updated packages from a central repository right after their release.

One of the basic concepts in the EZ template technology is the concept of 'repository' where software packages for the given EZ template are stored. A repository is a prepared directory or website containing the packages and index files for Linux operating systems and/or any of their applications. An example of such a repository is the repository located at the http://mirrors.usc.edu/pub/linux/distributions/fedora/ website and storing software packages for Fedora Core releases. Using repositories gives you the following advantages:

• Software packages included in the given EZ template do not contain versions, but only names (e.g. bash, crontabs). So, you always update any package included in the EZ template to its latest version available in the repository.
• As a result of the fact that a list of packages does not provide their versions, EZ templates do not have versions either (e.g. redhat-el5-x86). Thus, you install any EZ template on the host only once and, after that, use the installed template to update the packages inside any Container where it is applied.
• You can create several OS EZ template sets for one and the same Linux operating system. Any OS EZ template you are provided with has the default packages set included in it and is called the base OS EZ template. However, you can make your own OS EZ template sets (the so-called non-base OS EZ template sets) which may differ from the corresponding base template:
  • in the number of packages included in these EZ template sets
  • in the number and location of repositories to be used for these EZ template sets
  • in the number and kind of scripts to be executed on different EZ template sets life cycle stages

  Non-base OS EZ template sets must have their own names and are created by appending a random identifier to the base OS EZ template name. For example, if you wish your Container to run Red Hat Enterprise Linux 5 and to function as a Linux-based server only, you can create the redhat-el5-x86-server OS EZ template set and include only those packages in it that are needed for performing main server tasks. So, you can specify packages to be used for setting up file and print sharing and exclude all the packages for graphical interfaces (GNOME and KDE).

Virtuozzo provides you with a vzpkg tool allowing you to automatically locate and obtain the correct packages for your EZ templates from one or several package repositories. The packages are downloaded from the repository and installed on the host in one of the following cases:

• when creating a cache for an OS EZ template
• when updating an existing OS EZ template cache (if there are new packages available in the repository)
• when adding an application EZ template or package to the first Container
• when updating EZ templates or software packages inside a destination Container

Note: For details on how to manage software package repositories, see Setting Up Repository and Proxy Servers for EZ Templates.