Virtual Private Server User Guide

Internet and UNIX Basics

Your virtual server takes advantage of a technological development called Fast 

Flexible File Sharing (3FS). 3FS allows us to install most operating system files 

and preinstalled applications to a location that makes them available to all the 

VPS servers on the physical machine in a read only mode. We then install 

references to these files, called symbolic links, in your virtual disk in place of the 

actual files themselves. 

Each physical machine that houses a VPS server has a /usr/virtual/share directory 

that contains a copy of all of the files provided in a default account build. The 

contents of this directory are made available in a read only format to each 

account. 

Many of the files on your VPS server are actually symbolic links to files on the 

shared, read only filesystem. For example, /www/bin/httpd (our provided Apache 

Web server) is actually a symbolic link to the /usr/virtual/share/www/bin/httpd 

binary executable on the machine itself. There are hundreds of files that are 

shared in this way among all of the accounts on the host machine.

There are many benefits provided by 3FS, including:

   Because many of your files, applications and libraries are shared through 

3FS, we are able to provide a wealth of preinstalled software with minimal 

impact to your virtual disk. For example, a customer with a 300 MB virtual 

disk is in reality getting over 2 GB of preinstalled software with over 200 MB of 

free space left over!

   Updates, enhancements, and security fixes are much more quickly 

distributed to our customers.

   Although the files shared through 3FS would not normally need to be 

removed, replaced, or modified, 3FS is flexible enough to allow a customer 

with specific needs to do so. 

For example, /bin/perl (the Perl executable) and the default contents of the /usr/

local/lib/perl5 directory (our provided Perl modules) are shared through 3FS (they 

are symbolic links to /usr/virtual/share/bin/perl and the contents of /usr/virtual/

share/usr/local/lib/perl5 respectively). A customer with a need to install a 

bleeding edge Perl binary or Perl module and needs these to be located in the 

same locations occupied by our supported versions could delete the symbolic 

links and install his files in their place. 

It's important to note that the VPS that this customer exercised in this example 

comes with a price of responsibility:

   The files he installed use space on his virtual disk, whereas those in our 

default installation do not.

   When we update our default installation at a later date, his installation will not 

be updated.

   Our customer interface applications and "vtools," such as VAdmin, FATSI, 

vinstall, etc., may not work correctly, as they will always be written for our 

supported versions.

Technical Training Department

August 2004

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