Practical Cloud Knowledge: Install, Configure, and Manage - Deploying and Managing a Cloud Infrastructure - page 189

system. They are designed to be installed inside virtual machines after the guest operating
system has been installed. These tools are installed on guest OSs to expand their capabili-
ties, such as being able to share input devices and folders with the host easily and provide
virtual device drivers, better automation, and overall virtual machine performance gain.
The guest tools vary according to the cloud platform and service being used. For example,
we have VirtualBox Guest Additions, which can be installed on most guest operating systems
such as Windows and Linux using Oracle's VM VirtualBox.
Guest tools extend the functionality of your virtual machines but must be installed in a
special way because VMs will be typically dissociated from the host machine, meaning they
cannot access some of the host's accessories or peripheral devices out of the box until guest
tools are installed because they believe themselves to be a real machine independent of a
host. Some VMs have this functionality already, depending on the virtualization software
you are using, but it would be safer to assume that they don't.
The most common method of installing guest tools is through the use of virtual
CD-ROM drives. That is why most guest tools are distributed in the form of an ISO ( .iso )
file. Virtual drives can be created and attached to the virtual machine through the virtual-
ization manager you are using.
Installing guest tools is easier on some host systems than it is on others. For example,
using VMware Tools in VMware Server and Workstation using a Windows host is as
simple as going to the VM menu, clicking Install VMware Tools, and then following the
instructions in the installation wizard on the guest OS that pops up. This goes the same
for VirtualBox. However, for both systems, the installation of the guest tools in a Linux
host is more technical and requires more steps. But if you are familiar with the process, it
may take less than 10 minutes.
Snapshots and Cloning
Creating virtual machines from scratch would be quite tedious. That is why it is always
best to create them from prepared templates, unless of course you are aiming for a configu-
ration that has not yet been made into a template. But sometimes we just need a fast way
to create a virtual machine and be able to revert to a previous state for testing purposes
quickly and easily. This is where snapshots and cloning of virtual machines come in.
Snapshots As many of you may have already guessed, even though you might be not
entirely in the cloud computing field but are veterans in the general computing field, a snap-
shot is essentially a photo, a record of a specific state. In this case, a snapshot is a record
of a state of a virtual machine. The reason we take snapshots and not just create virtual
machines from a template is that even though we might have the entire configuration and
installed applications all set in a template, some forms of optimizations cannot be captured
in templates. It is therefore important to take a snapshot of the VM after doing a lot of
work to achieve the state it is in. If something goes wrong later, having a snapshot makes
it really easy to revert to that state of a virtual machine. This is handy not only for when
something goes wrong but also for comparing the performance of the VM before and after
certain alterations are made.
In Exercise 7.5, you'll create a snapshot.