As in cloud technology, virtualization plays an important role to make things easy and efficiently done, virtualization also need to be done at the OS level also. With the technique of virtualized OS, nothing is required to be pre-installed or permanently loaded on the local storage device. Everything runs from network using a virtual; simulation & that virtual disk is a disk-image (file) that remotely stored on a server i.e. Storage Area Network (SAN) or Non-Volatile Attached Storage (NAS).
Defining Operating System Virtualization
It is also called OS-level virtualization is a type of virtualization technology which work on OS layer. Here the kernel of an OS allows more than one isolated user-space instances to exist. Such instances are called containers/software containers or virtualization engines. In other words, OS kernel will run a single operating system & provide that operating system's functionality to replicate on each of the isolated partitions.
Uses of OS Virtualization
- Used for virtual hosting environment.
- Used for securely allocation of finite hardware resources among a large number of distrusting users.
- System administrator uses it to integrate server hardware by moving services on separate hosts.
- To improvised security by separating several applications to several containers.
- These forms of virtualization don't require hardware to work efficiently.
How OS Virtualization Works
The steps for how these virtualization works are listed below:
- Connect to OS Virtualization Server
- Connect to virtual disk
- Then connect this virtual disk to the client
- OS is streamed to the client
- If further additional streaming is required, it is done
General Types of OS Virtualization
Linux OS Virtualization
To virtualized Linux systems, VMware workstation software is used. To install any software virtually, users need VMware software to install first.
To create a virtual machine for Linux OS the steps to be followed are:
- Double click the VMware to run
- Click on "create new Virtual Machine"
- A window pops up, choose "custom" option and then click Next
- The next window appears, 'VM Hardware Compatibility window'; Click on Next button
- In the guest OS window pane - choose ISO image from the disk or any drive. Browse your ISO image & click Next
- A new window pops up waiting for username, password & confirm password to be feed in and then click Next
- In the processor configuration information, select your precise number of processor per core. If you want to keep the default setting > just ignore selecting and press Next
- The next window pops up to let user set memory limits. Put the value and click Next
- Next window let users set the disk size; then press Next
- In specify disk file window user can specify the disk file; then click Next
- In the last pop up window, click Finish.
- Now user will see a VMware screen then the OS's installation screen. And the installation will get started.
Windows OS Virtualization
Users need to install VMware first to install windows OS virtually.
After installing such virtualization software the steps to install a new OS are:
- Click on "create new Virtual Machine"
- Browse the OS that is to be installed, and click Next
- Give the product key if required; and click Next
- In the 'New Virtual Machine Wizard' window; click Next
- Give it a name & location and click Next
- The next step will create disk and the user can see the 1st Window screen.
- Select the version & OS architecture (64 bits or 86 bits)
- The Installation will be done
Advantages of OS Virtualization
- OS virtualization usually imposes little or no overhead.
- OS Virtualization is capable of live migration
- It can also use dynamic load balancing of containers between nodes and a cluster.
- The file level copy-on-write (CoW) mechanism is possible on OS virtualization which makes easier to back up files, more space-efficient and simpler to cache than the block-level copy-on-write schemes.
Virtual Disks in OS Virtualization
The client will be connected via the network to the virtual disk & will boot the OS installed on virtual disk. Two types of virtual disks are there for implementation.
- Private Virtual Disk: is used by one client only like that of a local hard disk. Users can save information on the virtual disk based on the rights assigned. So as the client restart the system, the settings are retained just like working with physical local hard disk.
- Shared/Common Virtual Disk: It is used by multiple clients at the same time. The changes are saved in a special cache & these caches gets cleaned as the user restarts or shutdowns the system. In other words, when a client is booting up, it will use the default configuration available on the virtual disk.