{"id":312,"date":"2017-12-29T14:25:52","date_gmt":"2017-12-29T14:25:52","guid":{"rendered":"https:\/\/bootstrap-it.com\/blog\/?p=312"},"modified":"2018-01-25T03:00:47","modified_gmt":"2018-01-25T03:00:47","slug":"aws-just-announced-a-move-from-xen-towards-kvm-so-what-is-kvm","status":"publish","type":"post","link":"https:\/\/bootstrap-it.com\/blog\/?p=312","title":{"rendered":"AWS just announced a move from Xen towards KVM. So what is KVM?"},"content":{"rendered":"
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Tied up in a recent AWS announcement about a new EC2 high-end instance type (the C5) is\u00a0a strong suggestion<\/a>\u00a0that Amazon\u2019s cloud computing giant has begun to shift its hundreds of thousands of physical servers away from the open source Xen hypervisor that\u2019s run them until now, to the open source alternative, KVM.<\/p>\n

Whether you\u2019ve got your career and\/or home mortgage deeply invested in the future of Xen or whether you never knew it existed, you might be interested in learning more about KVM. So here\u2019s a general introduction adapted from my book,\u00a0Teach Yourself Linux Virtualization and High Availability: prepare for the LPIC-3 304 certification exam<\/a>.<\/span><\/p>\n

Need some more basic background on either Linux servers or AWS? My\u00a0Linux in Action<\/a>\u00a0and\u00a0Learn Amazon Web Services in a Month of Lunches<\/a>\u00a0books from Manning might help, along with my\u00a0Linux server administration courses at Pluralsight<\/a>.<\/p><\/blockquote>\n

KVM<\/h4>\n

Like Xen, KVM (Kernel-based Virtual Machine) is an open source hypervisor technology for virtualizing compute infrastructure running on x86 compatible hardware. Also like Xen, KVM has both an active user community and significant enterprise deployments.<\/p>\n

A KVM host actually runs on the Linux\u00a0kernel<\/span>\u00a0along with two KVM kernel modules (the kvm.ko module and either kvm-intel.ko or kvm-amd.ko). Through its tight kernel integration\u200a\u2014\u200aincluding the I\/O connectivity with kernel block and network drivers provided by Virtio\u200a\u2014\u200aKVM can offer its guests more seamless access to all the complex hardware and networking profiles that they might encounter.<\/p>\n

Hardware virtualization extensions built into modern CPU designs and required for KVM deployments mean that, right out of the box, KVM guests can safely access only those hardware resources they need without the need to worry about leakage to the larger system.<\/p>\n

Where exactly does QEMU fit in with all this? Besides being able to act as a hypervisor, QEMU\u2019s strength is as an emulator. KVM, in its hypervisor virtualization role, can tap on to QEMU\u2019s emulation powers to compliment its own hardware acceleration features, presenting its guests with an emulated chipset and PCI bus. The whole, as they say, can be greater than the sum of its parts.<\/p>\n<\/div>\n

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A KVM hypervisor sitting between the Linux host OS and its guest\u00a0VMs<\/figcaption><\/figure>\n<\/div>\n
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A great deal of management functionality for KVM is often actually provided by Libvirt. Therefore, you might sometimes want to refer to the detailed information about KVM-related features like networking, storage, and file system layouts that\u2019s found in the fifth chapter of the\u00a0Teach Yourself Linux Virtualization and High Availability<\/a>\u00a0book (\u201cLibvirt and Related Tools\u201d).<\/p>\n

Installation<\/h4>\n

Before anything else, you\u2019ll need to make sure that the physical machine you\u2019re planning to use as a KVM host supports hardware virtualization. Besides the BIOS setting and the contents of \/proc\/cpuinfo (which we discussed in Chapter One), you can also quickly check this from a running Linux system using kvm-ok:<\/p>\n

$ kvm-ok<\/pre>\n
It\u2019s also a good idea to be sure which hardware architecture\u200a\u2014\u200a64 or 32-bit\u200a\u2014\u200ayou\u2019re working with:<\/p>\n
$ uname -m<\/pre>\n
But even if your hardware profile is up to the task, you\u2019ll have to let the Linux kernel in on your plans. If they\u2019re not already there, you should add the kvm and either kvm-intel or kvm-amd kernel modules.<\/p>\n
# modprobe kvm-intel<\/pre>\n
If those modules fail to load (and there\u2019s no \/dev\/kvm device in the file system), then there\u2019s a good chance your CPU just isn\u2019t up to the job you\u2019d like it to to. However, if all that worked out, you\u2019re ready to install the qemu-kvm package (and, if necessary, libvirt, virt-install, and bridge-utils as well).<\/p>\n
Working with KVM Management Tools<\/h4>\n
It\u2019s no secret that virtualization platforms have a well-deserved reputation for being complicated. But there are two things that can make getting started with KVM just a bit more challenging than some of the others:<\/p>\n