Installation guide

13
Templates Overview
EZ Templates Basics
All OS and application EZ templates are defined by the following features:
• EZ templates do not carry any package files. They contain only information about what
packages to install on the Hardware Node to make the templates fully operational and from
what network repository to download these packages.
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 Hardware Node. So, if the specified packages require
other packages to be installed, these packages are also downloaded from the repository and
installed on the Node. In case a package has requirements that conflict with existing software
on the Node 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
web site 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/ web site and storing software packages for
the 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
(for example, 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 (for example, centos-5-x86). Thus, you install any EZ template on
the Hardware Node 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 can 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 lifecycle
stages, etc.