KVM虚拟机的搭建过程
1. KVM安装
1.1 配置确认
首先需要确认服务器的硬件是否支持虚拟化，执行如下命令确认
root@DbackupServer:~# egrep -c '(svm|vmx)' /proc/cpuinfo
4
root@DbackupServer:~# 如果输出结果大于0，意味着服务器硬件是支持虚拟化的。否则，重启进入BIOS设置中启用VT技术。
执行如下命令安装kvm-ok程序，来确定服务器是否能够运行硬件加速的KVM虚拟机
root@Backup-standby:~# apt install cpu-checker
root@Backup-standby:~# kvm-ok
INFO: /dev/kvm exists
KVM acceleration can be used1.2 安装KVM
安装KVM及依赖项
#执行以下命令安装KVM
sudo apt update
#ubuntu 18
sudo apt install qemu qemu-kvm libvirt-bin bridge-utils virt-manager -y
#ubuntu 20
apt install qemu qemu-kvm bridge-utils virt-manager libvirt-daemon-system libvirt-clients virtinst libguestfs-tools cpu-checker -y
启动libvirtd服务，并设置开机自动启动
#将libvirtd添加自启动
sudo systemctl start libvirtd.service
sudo systemctl enable libvirtd.service执行service libvirtd status
查看libvirtd服务状态，如图
root@DbackupServer:/tmp# service libvirtd status
● libvirtd.service - Virtualization daemon
Loaded: loaded (/lib/systemd/system/libvirtd.service; enabled; vendor preset: enabled)
Active: active (running) since Fri 2021-12-10 17:16:00 CST; 10min ago
Docs: man:libvirtd(8)
https://libvirt.org
Main PID: 3699 (libvirtd)
Tasks: 19 (limit: 32768)
CGroup: /system.slice/libvirtd.service
├─3699 /usr/sbin/libvirtd
├─4479 /usr/sbin/dnsmasq --conf-file=/var/lib/libvirt/dnsmasq/default.conf --leasefile-ro --dhcp-script=/usr/lib/libvirt/libvirt_leaseshelper
└─4480 /usr/sbin/dnsmasq --conf-file=/var/lib/libvirt/dnsmasq/default.conf --leasefile-ro --dhcp-script=/usr/lib/libvirt/libvirt_leaseshelper
Dec 10 17:16:02 DbackupServer dnsmasq[4479]: compile time options: IPv6 GNU-getopt DBus i18n IDN DHCP DHCPv6 no-Lua TFTP conntrack ipset auth nettlehash DNSSEC loop-detect inotify
Dec 10 17:16:02 DbackupServer dnsmasq-dhcp[4479]: DHCP, IP range 192.168.122.2 -- 192.168.122.254, lease time 1h
Dec 10 17:16:02 DbackupServer dnsmasq-dhcp[4479]: DHCP, sockets bound exclusively to interface virbr0
Dec 10 17:16:02 DbackupServer dnsmasq[4479]: reading /etc/resolv.conf
Dec 10 17:16:02 DbackupServer dnsmasq[4479]: using nameserver 127.0.0.53#53
Dec 10 17:16:02 DbackupServer dnsmasq[4479]: read /etc/hosts - 5 addresses
Dec 10 17:16:02 DbackupServer dnsmasq[4479]: read /var/lib/libvirt/dnsmasq/default.addnhosts - 0 addresses
Dec 10 17:16:02 DbackupServer dnsmasq-dhcp[4479]: read /var/lib/libvirt/dnsmasq/default.hostsfile
Dec 10 17:16:02 DbackupServer dnsmasq[4479]: reading /etc/resolv.conf
Dec 10 17:16:02 DbackupServer dnsmasq[4479]: using nameserver 127.0.0.53#531.3 桥接网络配置
一般虚拟机网络配置有Bridge、NAT等几种模式。NAT模式下，虚拟机不需要配置自己的IP，通过宿主机来访问外部网络；Bridge模式下， 虚拟机需要配置自己的IP，然后虚拟出一个网卡， 与宿主机的网卡一起挂到一个虚拟网桥上（类似于交换机）来访问外部网络，这种模式下，虚拟机拥有独立的IP，局域网其它主机能直接通过IP与其通信。简单理解，就是NAT模式下，虚机隐藏在宿主机后面了，虚机能通过宿主机访问外网，但局域网其它主机访问不到它，Bridge模式下，虚机跟宿主机一样平等地存在，局域网其它主机可直接通过IP与其通信。一般我们创建虚机是用来部署服务供使用的， 所以都是用Bridge模式。
ubuntu 18中，网络配置通过netplan来实现了，如下，更改配置文件 etc/netplan/01-onenet-cfg.yaml
# This file describes the network interfaces available on your system
# For more information, see netplan(5).
network:
version: 2
renderer: networkd
ethernets:
ens160:
dhcp4: no
dhcp6: no
#addresses: [ 10.1.1.241/24 ]
#gateway4: 10.1.1.1
bridges:
br0:
dhcp4: no
dhcp6: no
addresses: [ 10.1.1.241/24 ]
gateway4: 10.1.1.1
interfaces: [ ens160 ]将宿主机原有网卡ens160挂到网桥br0上，并指定IP地址为10.1.1.241，nameservers指定DNS服务器。修改完后，通过sudo netplan apply
重启网络服务生效，然后通过ifconfig
查看，
root@DbackupServer:/tmp# ifconfig
br0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500
inet 10.1.1.241 netmask 255.255.255.0 broadcast 10.1.1.255
inet6 fe80::44b8:3dff:fead:79ec prefixlen 64 scopeid 0x20<link>
ether 46:b8:3d:ad:79:ec txqueuelen 1000 (Ethernet)
RX packets 1126973 bytes 4645823602 (4.6 GB)
RX errors 0 dropped 1 overruns 0 frame 0
TX packets 969044 bytes 65818318 (65.8 MB)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
ens160: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500
ether 00:0c:29:06:ae:a4 txqueuelen 1000 (Ethernet)
RX packets 10802871 bytes 15328761510 (15.3 GB)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 969044 bytes 65818318 (65.8 MB)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0原来挂在enp7s0网卡下的IP现在挂到了br0上，宿主机及所有其它虚拟机都通过该网桥来与外部通讯。我们也可以通过brctl show
来直观地查看，
root@DbackupServer:/tmp# brctl show
bridge name bridge id STP enabled interfaces
br0 8000.46b83dad79ec no ens160
virbr0 8000.525400e8cece yes virbr0-nic目前因为还没虚机，所以只有宿主机的网卡enp7s0挂在网桥br0上。同时也可以看到docker容器也是通过网桥docker0来通讯的。
2. 虚拟机安装
2.1 安装虚拟机
安装命令
sudo virt-install\
--name=CentOS-7\ #指定虚机名称
--memory=4096,maxmemory=4096\ #内存大小，单位Mb
--vcpus=2,maxvcpus=4\ #分配CPU
--os-type=linux\ #虚机类型
--os-variant=centos7.0\ #os版本，可通过osinfo-query os命令查询
--location=/home/CentOS-7-x86_64-DVD-1810.iso\ #镜像位置
--disk path=/infokist/centos7/CentOS-7.img,bus=virtio,size=50\ #虚机磁盘路径
--bridge=br0\
--graphics=none \
--console=pty,target_type=serial\
--extra-args="console=tty0 console=ttyS0,115200n8"其中–name指定虚机名称，后面可通过virsh管理；–memory=16384,maxmemory=16384配置了16G内存；–vcpus=4,maxvcpus=4配置了4个CPU内核；centos7需要制定–os-variant=rhel7；–disk path=xx,size=300制定了磁盘路径与大小，这里是300G。
如果执行上述命令出现qemu-kvm: could not open 'xx/CentOS-7-x86_64-DVD-1810.iso': Permission denied
异常退出时，可通过修改/etc/libvirt/qemu.conf
文件将user = "root"
，group = "root"
前面的注释去掉解决（https://github.com/jedi4ever/veewee/issues/996）
如无问题，安装程序将出现如下配置界面
Starting installer, one moment...
anaconda 21.48.22.147-1 for CentOS 7 started.
* installation log files are stored in /tmp during the installation
* shell is available on TTY2
* when reporting a bug add logs from /tmp as separate text/plain attachments
09:46:30 Not asking for VNC because we don't have a network
================================================================================
================================================================================
Installation
1) [x] Language settings 2) [!] Time settings
(English (United States)) (Timezone is not set.)
3) [!] Installation source 4) [!] Software selection
(Processing...) (Processing...)
5) [!] Installation Destination 6) [x] Kdump
(No disks selected) (Kdump is enabled)
7) [ ] Network configuration 8) [!] Root password
(Not connected) (Password is not set.)
9) [!] User creation
(No user will be created)
Please make your choice from above ['q' to quit | 'b' to begin installation |
'r' to refresh]: 可通过输入选项对应的数字来选择不同的配置，依次操作如下步骤完成时区设置：
输入2，回车，选择时区设置；输入1，回车，选择“Set timezone”；输入2，回车，选择“Asia”；回车，输入64，回车，选择“Shanghai”
1) [x] Language settings 2) [!] Time settings
(English (United States)) (Timezone is not set.)
3) [!] Installation source 4) [!] Software selection
(Processing...) (Processing...)
5) [!] Installation Destination 6) [x] Kdump
(No disks selected) (Kdump is enabled)
7) [ ] Network configuration 8) [!] Root password
(Not connected) (Password is not set.)
9) [!] User creation
(No user will be created)
Please make your choice from above ['q' to quit | 'b' to begin installation |
'r' to refresh]: 2然后进行安装设置，
依次操作如下：
1) [x] Language settings 2) [!] Time settings
(English (United States)) (Timezone is not set.)
3) [!] Installation source 4) [!] Software selection
(Processing...) (Processing...)
5) [!] Installation Destination 6) [x] Kdump
(No disks selected) (Kdump is enabled)
7) [ ] Network configuration 8) [!] Root password
(Not connected) (Password is not set.)
9) [!] User creation
(No user will be created)
Please make your choice from above ['q' to quit | 'b' to begin installation |
'r' to refresh]: 5输入5，回车，进入安装设置；输入c，回车，选择默认的磁盘进行安装；输入c，回车，使用默认的“2) Use All
Space”；输入1，回车，选择“1) Standard Partition”进行标准分区；输入c，回车，完成分区设置
最后进入root密码设置，
1) [x] Language settings 2) [!] Time settings
(English (United States)) (Timezone is not set.)
3) [!] Installation source 4) [!] Software selection
(Processing...) (Processing...)
5) [!] Installation Destination 6) [x] Kdump
(No disks selected) (Kdump is enabled)
7) [ ] Network configuration 8) [!] Root password
(Not connected) (Password is not set.)
9) [!] User creation
(No user will be created)
Please make your choice from above ['q' to quit | 'b' to begin installation |
'r' to refresh]: 8操作如下：
输入8，回车，进入root密码设置；输入密码，回车；输入确认密码，回车
1) [x] Language settings 2) [!] Time settings
(English (United States)) (Timezone is not set.)
3) [!] Installation source 4) [!] Software selection
(Processing...) (Processing...)
5) [!] Installation Destination 6) [x] Kdump
(No disks selected) (Kdump is enabled)
7) [ ] Network configuration 8) [!] Root password
(Not connected) (Password is not set.)
9) [!] User creation
(No user will be created)
Please make your choice from above ['q' to quit | 'b' to begin installation |
'r' to refresh]: b完成上述设置后，输入b开始进行安装
等待一段时间后，安装程序停在如下界面
Installing iwl6000-firmware (305/306)
Installing iwl135-firmware (306/306)
Performing post-installation setup tasks
Installing boot loader
.
Performing post-installation setup tasks
.
Configuring installed system
.
Writing network configuration
.
Creating users
.
Configuring addons
.
Generating initramfs
.
Running post-installation scripts
.
Use of this product is subject to the license agreement found at /usr/share/centos-release/EULA
Installation complete. Press return to quit
[anaconda] 1:main* 2:shell 3:log 4:storage-lo> Switch tab: Alt+Tab | Help: F1 按回车继续，最后输入用户名root，及前面设置的密码登录系统
[ OK ] Started Command Scheduler.
Starting Terminate Plymouth Boot Screen...
[ OK ] Started Dump dmesg to /var/log/dmesg.
[ OK ] Started Login Service.
[ 9.644263] ip6_tables: (C) 2000-2006 Netfilter Core Team
[ 9.713165] Ebtables v2.0 registered
[ 9.732869] IPv6: ADDRCONF(NETDEV_UP): eth0: link is not ready
[ 9.801317] nf_conntrack version 0.5.0 (16384 buckets, 65536 max)
[ 9.906933] bridge: filtering via arp/ip/ip6tables is no longer available by default. Update your scripts to load br_netfilter if you need this.
[ 9.929264] Netfilter messages via NETLINK v0.30.
[ 9.936897] ip_set: protocol 6
[ 14.084047] random: crng init done
CentOS Linux 7 (Core)
Kernel 3.10.0-957.el7.x86_64 on an x86_64
localhost login: 2.2 虚拟机网络配置
虚拟机安装完后，是没有分配IP的，我们通过ip a
命令查看，
这时候的eth0下面空空如也，什么都没有。在/etc/sysconfig/network-scripts/ifcfg-eth0
文件中添加如下内容
[root@localhost ~]# vi etc/sysconfig/network-scripts/ifcfg-eth0
TYPE=Ethernet
PROXY_METHOD=none
BROWSER_ONLY=no
BOOTPROTO=static
DEFROUTE=yes
IPV4_FAILURE_FATAL=no
IPV6INIT=yes
IPV6_AUTOCONF=yes
IPV6_DEFROUTE=yes
IPV6_FAILURE_FATAL=no
IPV6_ADDR_GEN_MODE=stable-privacy
NAME=eth0
UUID=67eb190e-8e63-4ffb-9c01-ff8478d17830
DEVICE=eth0
ONBOOT=yes #开机自启
IPADDR=10.1.1.243
PREFIX=24
GATEWAY=10.1.1.1
DNS1=10.1.1.1并通过systemctl restart network
重启网络生效，这时候再运行ip a
查看，eth0下面已经有配置的IP了。不出意外的话，局域网其它主机就可以通过该IP来远程SSH连接了。
[root@localhost network-scripts]# ip a
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
inet 127.0.0.1/8 scope host lo
valid_lft forever preferred_lft forever
inet6 ::1/128 scope host
valid_lft forever preferred_lft forever
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP group default qlen 1000
link/ether 52:54:00:e2:49:37 brd ff:ff:ff:ff:ff:ff
inet 10.1.1.243/24 brd 10.1.1.255 scope global noprefixroute eth0
valid_lft forever preferred_lft forever
inet6 fe80::882b:ec67:751b:40a9/64 scope link noprefixroute
valid_lft forever preferred_lft forever这时候我们再通过brctl show
来查看网桥挂载情况，br0下面已经多了一个vnet0虚拟网卡了。
root@DbackupServer:~# brctl show
bridge name bridge id STP enabled interfaces
br0 8000.46b83dad79ec no ens160
vnet0
virbr0 8000.525400e8cece yes virbr0-nic vethfe89039虚拟机装完后，默认的hostname是localhost，针对centos7，我们可以通过如下命令来修改hostname
[root@localhost ~]# hostnamectl set-hostname dev-server1然后在/etc/hosts文件中添加127.0.0.1的host映射 dev-server1
[root@localhost ~]# vi etc/hosts
127.0.0.1 localhost localhost.localdomain localhost4 localhost4.localdomain4 dev-server1
::1 localhost localhost.localdomain localhost6 localhost6.localdomain63. 虚拟机管理
列出当前运行的虚拟机
virsh listroot@DbackupServer:~# virsh list Id Name State ---------------------------------------------------- 4 CentOS-7 running如果列出所有的，则
virsh list --all从宿主机进入虚拟机
virsh console，后面接虚拟机ID或名称root@DbackupServer:~# virsh console 4 Connected to domain CentOS-7 Escape character is ^] CentOS Linux 7 (Core) Kernel 3.10.0-957.el7.x86_64 on an x86_64 localhost login: root Password: Last login: Fri Dec 10 18:00:08 on ttyS0 [root@localhost ~]#输入用户名，密码即可登录虚拟机，按
Ctrl+]
可退出。启动与关闭虚拟机
virsh start|shutdownroot@DbackupServer:~# virsh start CentOS-7 Domain CentOS-7 started root@DbackupServer:~# virsh shutdown 4 Domain 4 is being shutdownlibvirtd启动时，自动启动虚拟机
root@DbackupServer:~# virsh autostart CentOS-7 Domain CentOS-7 marked as autostarted挂起/恢复虚拟机
devuser@server_01:~$ virsh suspend dev-server1 # 挂起虚拟机 devuser@server_01:~$ virsh resume dev-server1 # 恢复挂起的虚销毁虚拟机
devuser@server_01:~$ virsh undefine dev-server1 # 彻底销毁虚拟机，会删除虚拟机配置文件，但不会删除虚拟磁盘查看虚拟机网卡类型
root@ubuntu-18:~# virsh domiflist c1 Interface Type Source Model MAC ------------------------------------------------------- vnet6 bridge br0 virtio 52:54:00:6c:bf:9f vnet7 network hostonly1 virtio 52:54:00:90:e9:8b添加新网卡
root@ubuntu-18:~# virsh attach-interface c1 --type network --source hostonly2 --model virtio Interface attached successfully root@ubuntu-18:~# virsh domiflist c1 Interface Type Source Model MAC ------------------------------------------------------- vnet6 bridge br0 virtio 52:54:00:6c:bf:9f vnet7 network hostonly1 virtio 52:54:00:90:e9:8b vnet25 network hostonly2 virtio 52:54:00:d3:60:1b加载配置文件
root@ubuntu-18:~# virsh attach-interface c1 --type network --source hostonly2 --model virtio --config Interface attached successfully root@ubuntu-18:~# virsh dumpxml c1 > /etc/libvirt/qemu/c1.xml root@ubuntu-18:~# virsh define /etc/libvirt/qemu/c1.xml Domain c1 defined from /etc/libvirt/qemu/c1.xml删除网卡
virsh detach-interface c1 --type network --mac 52:54:00:d3:60:1b --config
首先进入到图形界面
常用virsh指令:
1）virsh list 列出当前虚拟机列表，不包括未启动的
2）virsh list --all 列出所有虚拟机，包括所有已经定义的虚拟机
3）virsh destroy vm-name 关闭虚拟机
4）virsh start vm-name 启动虚拟机
5）virsh edit vm-name 编辑虚拟机xml文件
6）virsh undefine vm-name 删除虚拟机
7）virsh shutdown vm-name 停止虚拟机
8）virsh reboot vm-name 重启虚拟机
9）virsh autostart vm-name 虚拟机随宿主机启动
在完成kvm虚拟机的安装之后，如果想要重装相同名字的虚拟机，是会有错误提示的，就算是删除了虚拟机的xml文件，也会弹出错误提示。如下红色所注
[root@test-R410-4disk qemu]# virt-install --name=convirt --ram=512 --vcpus=2 --cpu=core2duo --pxe --os-type=linux --disk path=/data/vm/convirt.img,size=50 --network bridge=br1,model=virtio --network bridge=br0,model=virtio --graphics vnc,password=123456,port=9903 --hvm –force
ERROR Guest name 'convirt' is already in use.
这点kvm和xen不同，xen的半虚拟化要想重装，只要把创建好的虚拟机配置文件删掉就可以了
kvm如果想要重装相同名字的虚拟机，需要先关闭虚拟机
virsh destroy vm-name 关闭虚拟机
否则会有如下报错：
error:Failed to undefine domain test
error:Requested operationis not valid: cannot undefine transient domain
在虚拟机停止的状态下执行如下命令
[root@test-R410-4disk qemu]# virsh undefine convirt
Domain convirt has been undefined
这样，虚拟机就被干掉了，同样，相应的xml配置文件也干掉了。
然后在执行virt-install安装就不会报错了。