KVM Interview Preparation Guide

KVM module provides hardware acceleration for better performance and to provide better efficiency in between the virtual machines. To check the hardware acceleration checks the system configuration settings by using the following commands:

qemu-system-x86_64 -hda myvm.qcow2

If it gives any error message or module not find message then the modules are not loaded correctly.

KVM known as kernel virtual machine uses QEMU for device emulation. In this there are two networking modes that are defined. First mode is root networking mode and another mode is network bridge mode. If the IP address to the virtual machines has to be assigned then the kvm need to be up and running. To setup the network interface across the host machine the command that is required to be followed is as follows:

/sbin/ip
/usr/sbin/brctl
/usr/sbin/tunctl

KVM switch allows user to take control of two or more computers using the resources that are shared like mouse, keyboard, monitor, etc. This allows the administrator to access multiple servers from a single place. Administrator can access fileserver or internal server or proxy server and can separate out these servers from each other. This gives the freedom to administrator to use the components anywhere and make it efficient.

KVM switch is required to access more than one server from one place. The requirements of different switches differ from one institute to another. There are switches that give no protection but provide higher efficiency. Some switch offer the password to protect the switch. The password helps in locking the switch so that more security can be given. The switches provide protection to the user so that the data can be kept safe.

• Passive switch doesn't have any active components and it is a hard wired connection whereas, active switches are used to retain the actions performed by hardware devices that are connected during switching process.

• Passive switches are wired internally between Input/Output ports whereas, active switches uses the computers connection for their connections they don't rely on external or internal wires.

• Passive switches are simple and cheap whereas, active switches are a bit expensive in terms of its application and it requires separate power supplies.

• KVM is an internal part of the linux kernel module and uses regular memory and scheduler like linux, whereas Xen is an external hypervisor that takes the control and divides the resources between the guest machines.
• KVM is easy to use and provide more features, whereas Xen is powerful but it requires good amount of knowledge to operate.
• KVM runs on processors that support hvm, whereas Xen runs non-hvm compatible processors.
• KVM doesn't have any support for para-virtualization, whereas Xen supports para-virtualization that is used for device drivers to improve the performance of input/output.

KVM allow the resources to be shared to the guest operating systems. KVM allocates the memory dynamically between many processes. KVM allows the host to allocate the memory for the guest and beyond it guest can't use memory. The guest system that has a balloon driver keeps the guest from taking full memory. This ballooning is controlled by balloon monitor. KVM allows the pages that are similar to be grouped or collapse together in one to save the space this way the dynamic memory management can be performed by KVM.

KVM acts as a virtualization platform that is required by machines to run other operating system in synchronization with host operating system. It is an inbuilt virtualization platform that comes with Linux kernel. It is used for non-graphic servers and supports wide range of operating system to run with. It runs along with QEMU to provide strong virtualization platform.

To use KVM as a non-privileged user firs the creation of a group has to take place in which addition of the users takes places and then making their group. The file that has to be modified for the groups and by which the permissions can be set resides in /dev/kvm that has to be changed to give permissions to non-privileged users. To set the permission the following line has to be added or replaced in the file mentioned above.

KERNEL=="kvm", GROUP= "kvm"

KVM supports various formats in synchronization with QEMU as it supports many raw images, native QEMU format of qcow2, VMWare format like .vmx, .vmdk, etc. VirtualBox format like .vbx, etc. and many more. QEMU and KVM together give the advanced functionality to run virtualized servers and platforms.