Installation guide

12
Templates Overview
EZ Templates Overview
EZ templates are part and parcel of the Parallels Virtuozzo Containers philosophy because they
provide a way of sharing resources among lots of Containers, thus enabling huge savings in terms
of disk space and memory. For example, when you install and cache an OS template on the
Hardware Node, Parallels Virtuozzo Containers creates the
/vz/template/<name_of_the_OS> directory containing all the OS files that can be shared
among Containers. When a Container based on this template is created, it contains only symlinks
to the OS template files. These symlinks occupy very little space on the hard disk. They are situated
in the so-called private area of the Container. The corresponding directory is
/vz/private/<CT_ID>. The private area of a Container contains not only symlinks to the
necessary template files, but also the copy-on-write area of the Container (the area for storing the
information about those changes that the Container makes to the template files; this information
pertains only to the given directory) and all the private Container files. When the Container is
started, this private area is mounted as Virtuozzo File System (VZFS) to the /vz/root/<CT_ID>
directory. This directory is seen as the root directory from within the Container. And, which is the
pivot of it all, thanks to the VZFS, the symlinks of the Container private area are seen as real files
there!
Thus, the most important directories in the /vz partition are the following:
/vz/template - contains OS and application files shared among Containers;
/vz/private - contains VZFS symlinks to template files;
/vz/root - contains Container mounted symlinks and all other Container files.
The relation of these directories may be represented as below:
/vz/template (real files)  /vz/private (symlinks)  /vz/root (symlinks seen as real files
in / for the Container)
While you are able to perform all kinds of tasks within a Container including building RPM packages
and installing them, Parallels Virtuozzo Containers provides an easy and far more efficient way of
installing the applications you need inside Containers. In the same way as you install an OS
template on the Parallels Virtuozzo Containers system in order to create any number of Containers
on its basis and share its resources, you can install application templates in Parallels Virtuozzo
Containers in order to share application files among any number of Containers. You can then add
these applications to any number of Containers with a single command.