Basic management and operation of KVM virtual machine under Linux system
1. Check the local environment
1. Check the system version
[root@serer1 ~]# cat /etc/os-release
NAME="CentOS Linux"
VERSION="7 (Core)"
ID="centos"
ID_LIKE="rhel fedora"
VERSION_ID="7"
PRETTY_NAME="CentOS Linux 7 (Core)"
ANSI_COLOR="0;31"
CPE_NAME="cpe:/o:centos:centos:7"
HOME_URL="https://www.centos.org/"
BUG_REPORT_URL="https://bugs.centos.org/"
CENTOS_MANTISBT_PROJECT="CentOS-7"
CENTOS_MANTISBT_PROJECT_VERSION="7"
REDHAT_SUPPORT_PRODUCT="centos"
REDHAT_SUPPORT_PRODUCT_VERSION="7"
2. Check firewall status
[root@serer1 ~]# systemctl status firewalld
● firewalld.service - firewalld - dynamic firewall daemon
Loaded: loaded (/usr/lib/systemd/system/firewalld.service; disabled; vendor preset: enabled)
Active: inactive (dead) since Wed 2022-10-19 00:09:43 CST; 7s ago
Docs: man:firewalld(1)
Main PID: 642 (code=exited, status=0/SUCCESS)
3. Check selinux
[root@serer01 ~]# getenforce
Disabled
3. Check libvirtd service status
[root@server ~]# systemctl status libvirtd
● libvirtd.service - Virtualization daemon
Loaded: loaded (/usr/lib/systemd/system/libvirtd.service; enabled; vendor preset: enabled)
Active: active (running) since Sun 2022-10-16 17:53:24 CST; 2 days ago
Docs: man:libvirtd(8)
https://libvirt.org
Main PID: 29472 (libvirtd)
Tasks: 18 (limit: 32768)
Memory: 34.8M
CGroup: /system.slice/libvirtd.service
└─29472 /usr/sbin/libvirtd --listen
4. Check the kvm installation results
[root@server ~]# lsmod|grep kvm
kvm_intel 183621 4
kvm 586948 1 kvm_intel
irqbypass 13503 3 kvm
5. Check the kvm virtual machine status
[root@server ~]# virsh -c qemu:///system list
Id Name State
----------------------------------------------------
9 kvm01 running
6. Check virsh version
[root@server ~]# virsh --version
4.5.0
[root@server ~]# virt-install --version
1.5.0
Second, virsh common commands
1. List virtual machines
[root@server ~]# virsh list
Id Name State
----------------------------------------------------
9 kvm01 running
[root@server ~]# virsh list --all
Id Name State
----------------------------------------------------
9 kvm01 running
2. Virtual machine on/off operation
virsh start kvm01 # Virtual Machine Boot
virsh shutdown kvm01 # Close the virtual machine
virsh destroy kvm01 # Force stopping a virtual machine
3. Delete the virtual machine
virsh undefine kvm01 # Destroying the virtual machine completely will delete the virtual machine configuration file, but not the virtual disk
4. Set the virtual machine to start automatically when the host machine is turned on
virsh autostart kvm01 # Self-start when the host is turned on
virsh autostart --disable kvm01 # Take the power-on self-start
5. Suspend the virtual machine
virsh suspend kvm01 # Hanging a virtual machine
virsh resume kvm01 # Recovering a hung virtual machine
6. View the configuration file of the virtual machine
[root@server ~]# virsh dumpxml kvm01
<domain type='kvm' id='9'>
<name>kvm01</name>
<uuid>65438c9d-81cd-cd83-01de-77a5ed5af051</uuid>
<description>None</description>
<memory unit='KiB'>1048576</memory>
<currentMemory unit='KiB'>1048576</currentMemory>
<vcpu placement='static'>2</vcpu>
<resource>
<partition>/machine</partition>
</resource>
<os>
<type arch='x86_64' machine='pc-i440fx-rhel7.0.0'>hvm</type>
<boot dev='hd'/>
<boot dev='cdrom'/>
<bootmenu enable='yes'/>
</os>
<features>
<acpi/>
<apic/>
<pae/>
</features>
<cpu mode='custom' match='exact' check='full'>
<model fallback='forbid'>IvyBridge-IBRS</model>
<vendor>Intel</vendor>
<feature policy='disable' name='ds'/>
<feature policy='disable' name='acpi'/>
<feature policy='require' name='ss'/>
<feature policy='disable' name='ht'/>
<feature policy='disable' name='tm'/>
<feature policy='disable' name='pbe'/>
<feature policy='disable' name='dtes64'/>
<feature policy='disable' name='monitor'/>
<feature policy='disable' name='ds_cpl'/>
<feature policy='disable' name='vmx'/>
<feature policy='disable' name='est'/>
<feature policy='disable' name='tm2'/>
<feature policy='disable' name='xtpr'/>
<feature policy='disable' name='pdcm'/>
<feature policy='require' name='movbe'/>
<feature policy='disable' name='osxsave'/>
<feature policy='disable' name='arat'/>
<feature policy='disable' name='tsc_adjust'/>
<feature policy='require' name='rdseed'/>
<feature policy='require' name='smap'/>
<feature policy='require' name='clflushopt'/>
<feature policy='require' name='clwb'/>
<feature policy='disable' name='intel-pt'/>
<feature policy='require' name='sha-ni'/>
<feature policy='require' name='umip'/>
<feature policy='require' name='gfni'/>
<feature policy='disable' name='md-clear'/>
<feature policy='require' name='stibp'/>
<feature policy='require' name='ssbd'/>
<feature policy='require' name='xsaveopt'/>
<feature policy='require' name='xsavec'/>
<feature policy='require' name='xgetbv1'/>
<feature policy='require' name='3dnowprefetch'/>
<feature policy='disable' name='avx'/>
<feature policy='disable' name='f16c'/>
<feature policy='require' name='hypervisor'/>
</cpu>
<clock offset='utc'/>
<on_poweroff>destroy</on_poweroff>
<on_reboot>restart</on_reboot>
<on_crash>restart</on_crash>
<devices>
<emulator>/usr/libexec/qemu-kvm</emulator>
<disk type='file' device='disk'>
<driver name='qemu' type='qcow2'/>
<source file='/nas/kvm/centos_kvm.img'/>
<backingStore/>
<target dev='vda' bus='virtio'/>
<alias name='virtio-disk0'/>
<address type='pci' domain='0x0000' bus='0x00' slot='0x04' function='0x0'/>
</disk>
<disk type='file' device='cdrom'>
<driver name='qemu' type='raw'/>
<source file='/storage/kvm/CentOS-7-x86_64-Minimal-1511.iso'/>
<backingStore/>
<target dev='hda' bus='ide'/>
<readonly/>
<alias name='ide0-1-1'/>
<address type='drive' controller='0' bus='1' target='0' unit='1'/>
</disk>
<controller type='usb' index='0' model='piix3-uhci'>
<alias name='usb'/>
<address type='pci' domain='0x0000' bus='0x00' slot='0x01' function='0x2'/>
</controller>
<controller type='pci' index='0' model='pci-root'>
<alias name='pci.0'/>
</controller>
<controller type='ide' index='0'>
<alias name='ide'/>
<address type='pci' domain='0x0000' bus='0x00' slot='0x01' function='0x1'/>
</controller>
<interface type='bridge'>
<mac address='52:54:00:6c:cb:10'/>
<source network='br0' bridge='br0'/>
<target dev='vnet0'/>
<model type='virtio'/>
<alias name='net0'/>
<address type='pci' domain='0x0000' bus='0x00' slot='0x03' function='0x0'/>
</interface>
<serial type='pty'>
<source path='/dev/pts/0'/>
<target type='isa-serial' port='0'>
<model name='isa-serial'/>
</target>
<alias name='serial0'/>
</serial>
<console type='pty' tty='/dev/pts/0'>
<source path='/dev/pts/0'/>
<target type='serial' port='0'/>
<alias name='serial0'/>
</console>
<input type='mouse' bus='ps2'>
<alias name='input0'/>
</input>
<input type='tablet' bus='usb'>
<alias name='input1'/>
<address type='usb' bus='0' port='1'/>
</input>
<input type='keyboard' bus='ps2'>
<alias name='input2'/>
</input>
<graphics type='vnc' port='5900' autoport='yes' listen='0.0.0.0'>
<listen type='address' address='0.0.0.0'/>
</graphics>
<video>
<model type='cirrus' vram='16384' heads='1' primary='yes'/>
<alias name='video0'/>
<address type='pci' domain='0x0000' bus='0x00' slot='0x02' function='0x0'/>
</video>
<memballoon model='virtio'>
<alias name='balloon0'/>
<address type='pci' domain='0x0000' bus='0x00' slot='0x05' function='0x0'/>
</memballoon>
</devices>
<seclabel type='dynamic' model='dac' relabel='yes'>
<label>+107:+107</label>
<imagelabel>+107:+107</imagelabel>
</seclabel>
</domain>
7. Operation on the virtual machine configuration file
virsh edit vm-name # Modify the configuration file of the virtual machine
virsh define file-name.xml # Define the virtual machine according to the configuration file
8. View KVM virtual machine related configuration files
[root@server ~]# ls /etc/libvirt/qemu/
autostart kvm01.xml networks
[root@server ~]# ls /etc/libvirt/qemu/networks/
autostart br0.xml
[root@server ~]# ls /etc/libvirt/qemu/networks/autostart/
br0.xml
3. Disk management of KVM virtual machine
1. Check the disk format
[root@server ~]# qemu-img info /nas/kvm/centos_kvm.img
image: /nas/kvm/centos_kvm.img
file format: qcow2
virtual size: 40G (42949672960 bytes)
disk size: 2.2G
cluster_size: 65536
Format specific information:
compat: 0.10
2. Convert the raw format disk file to qcow2
$ qemu-img convert -f raw -O qcow2 /data/centos7.raw /data/centos7.qcow
# qemu-img covert -f Source format -O Destination format Source disk file Destination disk file
3. Create an empty disk file in qcow2 format
[root@server kvm]# qemu-img create -f qcow2 /nas/kvm/test.qcow2 5G
Formatting '/nas/kvm/test.qcow2', fmt=qcow2 size=5368709120 encryption=off cluster_size=65536 lazy_refcounts=off
[root@server kvm]# qemu-img info /nas/kvm/test.qcow2
image: /nas/kvm/test.qcow2
file format: qcow2
virtual size: 5.0G (5368709120 bytes)
disk size: 196K
cluster_size: 65536
Format specific information:
compat: 1.1
lazy refcounts: false
4. Modify the image file size
[root@server kvm]# qemu-img resize ./test.qcow2 +7G
Image resized.
[root@server kvm]# qemu-img info /nas/kvm/test.qcow2
image: /nas/kvm/test.qcow2
file format: qcow2
virtual size: 12G (12884901888 bytes)
disk size: 200K
cluster_size: 65536
Format specific information:
compat: 1.1
lazy refcounts: false
5. Add a new hard disk to the virtual machine - take effect temporarily
virsh attach-disk kvm01 /nas/kvm/test.qcow2 vdb --subdriver=qcow2
# virsh attach-disk <virtual machine name> <addition disk path> <device name> <disk format type>
6. Add a new hard disk to the virtual machine - permanent effect
virsh attach-disk kvm01 /nas/kvm/test.qcow2 vdb --subdriver=qcow2 --config
7. Unmount the hard drive
virsh detach-disk kvm01 /nas/kvm/test.qcow2 #卸载临时生效
virsh detach-disk kvm01 /nas/kvm/test.qcow2 --config # 卸载永久生效
8. Check the virtual machine hardware
[root@server kvm]# virsh dumpxml kvm01 |grep dev
<boot dev='hd'/>
<boot dev='cdrom'/>
<devices>
<disk type='file' device='disk'>
<target dev='vda' bus='virtio'/>
<disk type='file' device='disk'>
<target dev='vdb' bus='virtio'/>
<disk type='file' device='cdrom'>
<target dev='hda' bus='ide'/>
<target dev='vnet0'/>
<source path='/dev/pts/0'/>
<console type='pty' tty='/dev/pts/0'>
<source path='/dev/pts/0'/>
</devices>
9. View new virtual machine hard disks on WebVirtMgr
Four, KVM virtual machine network card management
1. Check the network card
[root@server kvm]# virsh domiflist kvm01
Interface Type Source Model MAC
-------------------------------------------------------
vnet0 bridge br0 virtio 52:54:00:6c:cb:10
2. Add network card
[root@server kvm]# virsh attach-interface kvm01 --type bridge --source br0
Interface attached successfully
3. Make the new network card take effect
[root@server kvm]# virsh dumpxml kvm01 > /etc/libvirt/qemu/kvm01.xml
[root@server kvm]# virsh define /etc/libvirt/qemu/kvm01.xml
Domain kvm01 defined from /etc/libvirt/qemu/kvm01.xml
4. View the newly added network card in the virtual machine
[root@server kvm]# ssh root@192.168.3.169
The authenticity of host '192.168.3.169 (192.168.3.169)' can't be established.
ECDSA key fingerprint is SHA256:SMUWtN77SI+zUIX2bBR7/hY176zJLiWvY7KpIUlK0dw.
ECDSA key fingerprint is MD5:df:58:7e:61:73:82:b5:56:03:25:60:f1:80:a6:b1:0b.
Are you sure you want to continue connecting (yes/no)? yes
Warning: Permanently added '192.168.3.169' (ECDSA) to the list of known hosts.
root@192.168.3.169's password:
Last login: Tue Oct 18 23:19:15 2022 from 192.168.3.11
[root@serer01 ~]# ip add
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN
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 qlen 1000
link/ether 52:54:00:6c:cb:10 brd ff:ff:ff:ff:ff:ff
inet 192.168.3.169/24 brd 192.168.3.255 scope global eth0
valid_lft forever preferred_lft forever
inet6 fe80::5054:ff:fe6c:cb10/64 scope link
valid_lft forever preferred_lft forever
3: docker0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP
link/ether 02:42:5d:4a:c4:9f brd ff:ff:ff:ff:ff:ff
inet 172.17.0.1/16 brd 172.17.255.255 scope global docker0
valid_lft forever preferred_lft forever
inet6 fe80::42:5dff:fe4a:c49f/64 scope link
valid_lft forever preferred_lft forever
5: veth0604e80@if4: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue master docker0 state UP
link/ether be:7f:bd:57:88:71 brd ff:ff:ff:ff:ff:ff link-netnsid 0
inet6 fe80::bc7f:bdff:fe57:8871/64 scope link
valid_lft forever preferred_lft forever
6: ens7: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN qlen 1000
link/ether 52:54:00:45:1b:53 brd ff:ff:ff:ff:ff:ff
5. Delete the network card
You need to shut down the virtual machine and then delete the network card
[root@server kvm]# virsh detach-interface kvm01 --type bridge --mac 52:54:00:45:1b:53 --config
Interface detached successfully
[root@server kvm]# virsh dumpxml kvm01 > /etc/libvirt/qemu/kvm01.xml
[root@server kvm]# virsh define /etc/libvirt/qemu/kvm01.xml
Domain kvm01 defined from /etc/libvirt/qemu/kvm01.xml
[root@server kvm]# virsh domiflist kvm01
Interface Type Source Model MAC
-------------------------------------------------------
- bridge br0 virtio 52:54:00:6c:cb:10
5. Snapshot management of KVM virtual machine
1. Create a snapshot
[root@server kvm]# virsh snapshot-create kvm01
Domain snapshot 1666155063 created
2. View the snapshot list
[root@server kvm]# virsh snapshot-list kvm01
Name Creation Time State
------------------------------------------------------------
1666155063 2022-10-19 12:51:03 +0800 shutoff
3. View snapshot information
[root@server kvm]# virsh snapshot-info kvm01 --current
Name: 1666155063
Domain: kvm01
Current: yes
State: shutoff
Location: internal
Parent: -
Children: 0
Descendants: 0
Metadata: yes
4. View snapshot directory
[root@server kvm]# ll /var/lib/libvirt/qemu/snapshot/
total 0
drwxr-xr-x 2 root root 28 Oct 19 12:51 kvm01
[root@server kvm]# ll /var/lib/libvirt/qemu/snapshot/kvm01/
total 8
-rw------- 1 root root 5550 Oct 19 12:51 1666155063.xml
5. Delete snapshots
[root@server kvm]# virsh snapshot-delete kvm01 1666155063
Domain snapshot 1666155063 deleted
6. Restoring a Snapshot
virsh snapshot-revert kvm01 1666155063 --running
7. snapshot-revert usage
snapshot-revert用法：snapshot-revert <domain> [<snapshotname>] [–current] [–running] [–paused] [–force]
Options.
[--domain] <string> : Specify the domain name, id or uuid
[--snapshotname] <string> : Specify the snapshot name
--current : Restore to the current snapshot
--running : Automatically run the virtual machine after resuming the snapshot
--paused : Automatically suspend the virtual machine after resuming the snapshot
--force : force snapshot, risky recovery option