CentOS7安装KVM虚拟化

一、KVM介绍

KVM，基于内核的虚拟机（英语：Kernel-based Virtual Machine，缩写为 KVM），

是一种用于Linux内核中的虚拟化基础设施，可以将Linux内核转化为一个hypervisor。

二、KVM部署及使用

1.系统环境查询

[root@localhost ~]# cat /etc/redhat-release
CentOS Linux release 7.5.1804 (Core) 
[root@localhost ~]# uname -r
3.10.0-862.el7.x86_64
[root@localhost ~]# sestatus
SELinux status:                 enabled
SELinuxfs mount:                /sys/fs/selinux
SELinux root directory:         /etc/selinux
Loaded policy name:             targeted
Current mode:                   permissive
Mode from config file:          enforcing
Policy MLS status:              enabled
Policy deny_unknown status:     allowed
Max kernel policy version:      31


验证CPU是否支持虚拟化，输入有vmx或svm就支持，支持虚拟化则就支持KVM
[root@localhost ~]# cat /proc/cpuinfo | egrep 'vmx|svm'

有vmx或svm内容输出就支持，支持虚拟化则就支持KVM

查看是否加载KVM

　[root@promote images]# lsmod | grep kvm

　kvm_intel 174841 0
　kvm 578518 1 kvm_intel
　irqbypass 13503 1 kvm

　已经加载，如果没有加载，则执行以下命令，加载KVM

　[root@localhost ~]#modprobe kvm

配置网卡桥接，原来的主机网卡配置文件内容修改如下： 

BOOTPROTO=none
DEVICE=enp2s0f0
#NM_CONTROLLED=no
ONBOOT=yes
#TYPE=Ethernet
#USERCTL=no
#IPADDR=45.141.44.2
#NETMASK=255.255.255.0
#GATEWAY=45.141.44.1
#DNS1=8.8.8.8
BRIDGE=br0

只需要以上内容就行了，不要再多内容，不然可能会启动不了网卡，导致主机无法远程。

下面是br0桥接网卡内容。

DEVICE=br0
TYPE=Bridge
ONBOOT=yes
NM_CONTROLLED=yes
BOOTPROTO=static
IPADDR=45.141.44.2
NETMASK=255.255.255.0
GATEWAY=45.141.44.1
DNS1=8.8.8.8

配置好网卡配置文件后，可以停用防火墙与sellinux。

sed -i 's/SELINUX=enforcing/SELINUX=disabled/g' /etc/selinux/config

systemctl disable firewalld.service
systemctl stop firewalld.service
echo "net.ipv4.ip_forward = 1" >>/etc/sysctl.conf

重启网卡只能使用这个命令，不能使用netowrk,不然会有问题，两都有冲突。

systemctl restart NetworkManager.service
或是直接重启系统。

2.安装KVM虚拟化软件

安装依赖包(使用本地yum源)

# yum install libvirt* virt-* qemu-kvm* -y
# yum -y install qemu-kvm qemu-kvm-tools qemu-img virt-manager libvirt libvirt-python libvirt-client bridge-utils virt-viewer virt-install 

说明：

libvirt    # 虚拟机管理
virt       # 虚拟机安装克隆
qemu-kvm   # 管理虚拟机磁盘

启动KVM

# systemctl start libvirtd.service
# systemctl status libvirtd.servic

2.安装第一台KVM虚机

[root@localhost ~]# virt-install --name centos6.5_1 --ram 800 --vcpus 1 
--disk path=/home/vmdisk/cnetos6.5_1.qcow2,format=qcow2,size=10 
--network=bridge=br0 --cdrom=/opt/CentOS-6.5-x86_64-minimal.iso  
--os-type=linux --autostart --vnclisten=0.0.0.0 --vncport=6900 --vnc
新建一个centos6.5的虚拟机,开通VNC远程端口6900，内存 800M,硬盘为10GB，
网卡采用桥接br0形式的虚拟机。

[root@localhost ~]# virt-install 
--virt-type kvm 
--os-type=linux 
--os-variant rhel7 
--name centos7 
--memory 1024 
--vcpus 1 
--disk (虚拟硬盘绝对路径),format=raw,size=10 
--cdrom (iso镜像文件绝对路径) 
--network network=default 
--noautoconsole

注意：需要先将镜像文件拷贝到 设置的路径下

参数说明

3.KVM虚机管理

virsh命令常用参数总结

查看虚拟机配置文件

[root@localhost ~]# cat /etc/libvirt/qemu/test01.xml

修改KVM虚拟机配置的方法

[root@localhost ~]# virsh edit test01　　　　(使用该命令修改可以对文件进行语法校验)

Running virt-install to Build the KVM Guest System

The virt-install utility must be run as root and accepts a wide range of command-line arguments that are used to provide configuration information related to the virtual machine being created. Some of these command-line options are mandatory (specifically name, ram and disk storage must be provided) while others are optional. A summary of these arguments is outlined in the following table:

An Example CentOS virt-install Command

With reference to the above command-line argument list, we can now look at an example command-line construct using the virt-install tool.

The following command creates a new KVM virtual machine configured to run Windows 7 using full virtualization. It creates a new, 10GB disk image, assigns 512MB of RAM to the virtual machine, configures a CD device for the installation media and uses VNC to display the console:

virt-install --name myWin7 –-hvm --ram 512 --disk path=/tmp/win7.img,size=10 
--network network:default --vnc --os-variant vista --cdrom /dev/hda

Note that the above command line assumes the installation media is in a drive corresponding to device file /dev/hda. This may differ on your system, or may be replaced by a path to an ISO image file residing on a file system.

As the creation process runs, the virt-install command will display status updates of the creation progress:

Starting install...
Creating storage file...                                 | 6.0 GB     00:00
Creating domain...                                       |    0 B     00:00
Domain installation still in progress. Waiting for installation to complete.

Install KVM Hypervisor on CentOS 7.x and RHEL 7.x

KVM is an open source hardware virtualization software through which we can create and run multiple Linux based and windows based virtual machines simultaneously. KVM is known as Kernel based Virtual Machine because when we install KVM package then KVM module is loaded into the current kernel and turns our Linux machine into a hypervisor.

In this post first we will demonstrate how we can install KVM hypervisor on CentOS 7.x and RHEL 7.x and then we will try to install virtual machines.

Before proceeding KVM installation, let’s check whether your system’s CPU supports Hardware Virtualization.

Run the beneath command from the console.

[root@linuxtechi ~]# grep -E '(vmx|svm)' /proc/cpuinfo

We should get the word either vmx or svm in the output, otherwise CPU doesn’t support virtualization.

Step:1 Install KVM and its associate packages

Run the following yum command to install KVM and its associated packages.

[root@linuxtechi ~]# yum install qemu-kvm qemu-img virt-manager libvirt libvirt-python libvirt-client virt-install virt-viewer bridge-utils

Start and enable the libvirtd service

[root@linuxtechi ~]# systemctl start libvirtd
[root@linuxtechi ~]# systemctl enable libvirtd

Run the beneath command to check whether KVM module is loaded or not

[root@linuxtechi ~]# lsmod | grep kvm
kvm_intel             162153  0
kvm                   525409  1 kvm_intel
[root@linuxtechi ~]#

In Case you have Minimal CentOS 7 and RHEL 7 installation , then virt-manger will not start for that you need to install x-window package.

[root@linuxtechi ~]# yum install "@X Window System" xorg-x11-xauth xorg-x11-fonts-* xorg-x11-utils -y

Reboot the Server and then try to start virt manager.

Step:2 Start the Virt Manager

Virt Manager is a graphical tool through which we can install and manage virtual machines. To start the virt manager type the ‘virt-manager‘ command from the terminal.

[root@linuxtechi ~]# virt-manager

Step:3 Configure Bridge Interface

Before Start creating VMs , let’s first create the bridge interface. Bridge interface is required if you want to access virtual machines from outside of your hypervisor network.

[root@linuxtechi ~]# cd /etc/sysconfig/network-scripts/
[root@linuxtechi network-scripts]# cp ifcfg-eno49 ifcfg-br0
[root@linuxtechi network-scripts]#

Edit the Interface file and set followings:

[root@linuxtechi network-scripts]# vi ifcfg-eno49
TYPE=Ethernet
BOOTPROTO=static
DEVICE=eno49
ONBOOT=yes
BRIDGE=br0

Edit the Bridge file (ifcfg-br0) and set the followings:

[root@linuxtechi network-scripts]# vi ifcfg-br0
TYPE=Bridge
BOOTPROTO=static
DEVICE=br0
ONBOOT=yes
IPADDR=192.168.10.21
NETMASK=255.255.255.0
GATEWAY=192.168.10.1
DNS1=192.168.10.11

Replace the IP address and DNS server details as per your setup.

Restart the network Service to enable the bridge interface.

[root@linuxtechi ~]#  systemctl restart NetworkManager.service
[root@linuxtechi ~]#

Check the Bridge interface using below command :

[root@linuxtechi ~]# ip addr show br0

Step:4 Start Creating Virtual Machines.

Now Create Virtual Machine either from the command line using ‘virt-install‘ command or from GUI (virt-manager )

Let’s Create a virtual machine of “Windows Server 2012 R2” using virt-manager.

Start the “virt-manager”

Go to the File Option, click on “New Virtual Machine”

We will be using ISO file as installation media. In the next step Specify the path of ISO file.

Click on Forward.

Specify the Compute Resources : RAM and CPU as per your setup.

Click on Forward to proceed further.

Specify the storage Size of Virtual Machine, In my case I am using 25G.

In the Next step Specify the Name of Virtual Machine and select network as ‘ Bridge bro’

Click on Finish to start the installation.

Follow the screen instructions and complete the installation.

Creating a virtual Machine from Command Line:

Virtual Machines can be created from the console as well using ‘virt-install’ command. In the following example i going to virtual machine of Ubuntu 16.04 LTS.

[root@linuxtechi ~]# virt-install --name=Ubuntu-16-04 --file=/var/lib/libvirt/images/ubuntu16-04.dsk --file-size=20 --nonsparse --graphics spice --vcpus=2 --ram=2048 --cdrom=ubuntu-16.04-server-amd64.iso --network bridge=br0 --os-type=linux --os-variant=generic
Starting install...
Allocating 'ubuntu16-04.dsk'               | 20 GB 00:00:00
Creating domain...

Follow the instruction now and complete the installation.

In the above ‘virt-install’ command we have used following options :

• –name = <Name of the Virtual Machine>
• –file = <Location where our virtual machine disk file will be stored >
• –file-size = < Size of the Virtual Machine, in my case it is 20GB >
• –nonsparse = < Allocate the whole storage while creating>
• –graphics = < Specify the graphical tool for interactive installation, in above example I am using spice >
• –vcpu = < Number of virtual CPU for the Machine >
• –ram = < RAM size for the virtual Machine >
• –cdrom = < Virtual CD ROM which specify the installation media like ISO file >
• –network = < it is used to specify which network we will use for the virtual machine, in this example I am bridge interface>
• –os-type = < Operating system type like linux and window>
• –os-variant= <KVM maintains the OS variants like ‘fedora18′, ‘rhel6’ and ‘winxp’ , this option is optional and if you not sure about OS variant you can mentioned it as generic>

Once the Installation is completed we can access the Virtual Machine console from ‘virt-manager‘ as shown below.

That’s it, basic installation and configuration of KVM hypervisor is completed.

Virtualization in Linux: Installing KVM on CentOS & RHEL

In this tutorial, we will be installing KVM on CentOS or RHEL machines. KVM (also called QEMU) or Kernel Based Virtualization Machine is a Hardware based virtualization software that provide a Linux system capability to run multiple operating systems in Linux environment. It can run Linux as well as Windows family OS.

By hardware based virtualization, it means that your processor must support hardware virtualization to run KVM on your system. So if your processor is Intel based, it must support Intel VT or if you are using AMD based processor, it must support AMD-V. So before we proceed further with this tutorial we must check if your processor supports hardware virtualization or not. Most of the modern processors do support hardware virtualization but to be sure, please run the following command,

If you receive ‘vmx or svm’ in the output than processor supports hardware virtualization otherwise it doesn’t support it & you can’t install KVM/QEMU on your machine.

KVM/QEMU can be managed either graphically or through CLI. We use virt-manager for managing virtual machines, it can create, delete, edit & can also cold/live migrate guest machines between hosts.

Installing KVM on CentOS or RHEL

For installing KVM, run the following command,

Now, let’s have a brief look at what these packages actually are,

• qemu-kvm is QEMU emulator, it’s the main package for KVM,
• qemu-img is QEMU disk image manager,
• virt-install is a command line tool to create virtual machines.
• libvirt , it provides daemon to manage virtual machines and controls hypervisor.
• libvirt-client , it provides client side API’s for accessing servers and virsh utility which provides command line tool to manage virtual machines.
• virt-viewer is the graphical console.

QEMU is now ready, we will now restart our virtualization daemon called ‘libvertd’,

We will now create virtual machine with the help of virt-manager. But before we start with creating a virtual machine, we will have to configure a bridge adapter, which is required if we need to access outside network from our VM.

Creating a Bridge adapter

Copy file for your current network interface ‘ifcfg-en0s1’ to another file for bridge interface named ‘ifcfg-br0’

Now we will edit the file ‘ifcfg-br0’,

Change network settings as per your own network requirements. Save the file & restart network services.

Now let’s create our first virtual machine.

Creating a Virtual Machine

We will launch ‘virt-manager’ to create our first virtual machine. You can launch viet-manager either using CLI or graphically,

For CLI, launch your terminal & type

Or Virtual machine manager in you Application under system tools. Once it has been launched, goto ‘File’ & click on ‘New Virtual Machine’

We will be using an ISO image for our installation, so select ‘Local Install Media’ for installing OS,

next , select the location for your ISO image & click Forward,

on the next page, select ‘Memory’ & number of ‘CPUs’ & click Forward,

specify the storage size for your VM & click Forward,

On the next page will be the summary for our VM, review all the configurations & in Network selection , select bridged adapter ‘br0’ & hit finish. Now install the OS as you normally do & boot into VM once the installation has been completed. Similarly create as many VMs as you need & as your resources permit.

This concludes our tutorial for installing KVM on CentOS. if you are having any issues or have any suggestions, please feel free to submit them through comment box down below.