=====KVM=====

====Install====

  apt-get install qemu-kvm virtinst virt-manager bridge-utils libosinfo-bin
  apt install -y qemu qemu-kvm libvirt-daemon libvirt-clients bridge-utils virt-manager    #ubuntu 20.04

  sudo adduser $USER kvm 
  #apt-get install qemu-kvm libvirt-bin virtinst bridge-utils cpu-checker
  sudo kvm-ok                                                                       #check      

  systemctl status libvirtd.service

  https://github.com/LuyaoHuang/virsh-bash-completion                               #bash completion
  
====Network====

Set your network devices on OS level such as (example with 2 network interfaces "enp4s0" and "eno1" which is bridge slave interface for bridge "vmbr0"):

<code>
# This file describes the network interfaces available on your system
# For more information, see netplan(5).
network:
 version: 2
 renderer: networkd
 ethernets:
   enp4s0:
     dhcp4: no
     dhcp6: no
     addresses: [192.168.1.100/24]
     gateway4: 192.168.1.1
     mtu: 1500
     nameservers:
       addresses: [192.168.1.1]
       search: [local]
   eno1:
     dhcp4: no
     dhcp6: no
 bridges:
   vmbr0:
     dhcp4: no
     dhcp6: no
     interfaces: [eno1]
     addresses: [10.0.0.100/24]
     gateway4: 10.0.0.1
     mtu: 1500
     #nameservers:
     #  addresses: [8.8.8.8,8.8.4.4]
     #parameters:
     #  stp: true
     #  forward-delay: 4
</code>
====Commands====

  virsh list                                                       #show running vm´s
  virsh list --all                                                 #show all vm´s 
  virsh undefine vm1
  virsh destroy vm1                                                #forcefully and immediately stop a given domain - the vm won´t be destoyed, just stopped.
  virsh start vm-name
  virsh autostart test                                             #
  virsh reboot vm-name
  virsh shutdown vm-name
  virsh suspend vm-name
  virsh resume vm-name
  virsh domrename foo bar                                          #rename vm from foo to bar
  virsh autostart vm-name
  virsh autostart --disable vm-name
  virsh domrename $OLD_NAME $NEW_NAME
  virsh domrename --domain oldname newname                         #rename domain/ vm       
  virsh edit vm-name                                               #edit vm properties
  osinfo-query os                                                  #list available os when specify os by "--os-variant" - package "libosinfo-bin" is required!
  virsh net-list                                                   #list running network configs
  virsh net-list --all                                             #list all network configs
  virsh dumpxml vm-name                                            #xml-config to stdout
  virsh dumpxml master > master.xml                                #backup vm
  virsh define master.xml                                          #restore vm 
  virt-manager                                                     #gui to show, manage and create vm´s
====snapshot====
  virsh snapshot-list vm-name                                                 #list all snaps       
  virsh snapshot-list vm-name--tree 
  virsh snapshot-create-as vm-name
  virsh snapshot-create-as --domain vm-name --name snap-name
  virsh snapshot-create-as vm-name
  virsh snapshot-create-as vm-name "snap1" --diskspec sda,file=/var/backups/snapshots/snap1-vm-name.qcow2 --disk-only --atomic
  virsh snapshot-info --domain vm-name --snapshotname snap-name
  virsh snapshot-revert --current vm-name
  virsh snapshot-delete --current vm-name
  virsh snapshot-delete --domain vm-name --snapshotname snap-name
  virsh snapshot-create-as --disk-only vm-name
  virsh snapshot-edit --rename  --domain vm-name --snapshotname snap-name     #rename
  virsh snapshot-delete --current --metadata vm-name                          #delete "disk-snapshot"
  qemu-img info --backing-chain test.qcow2
  qemu-img info test.qcow2
  qemu-img convert -O output_format source destination
  virsh domblklist vm-name
  virsh blockcommit vm-name sda --active --verbose --pivot

===Change Path Of "backing file"===

<code sh rename-backup-path.sh>
#!/bin/bash

BACKINGFILE="/kvm/images/master.qcow2"
QCOW2_FILE_TO_CHANGE="master.1586464836"

sudo qemu-img rebase \
  -f qcow2 \
  -u \
  -b $BACKINGFILE \
  $QCOW2_FILE_TO_CHANGE
</code>

Other:

<code>
sudo qemu-img rebase \
  -f qcow2 \
  -b $NEW_BACKING_FILE \
  $QCOW2_FILE_TO_CHANGE
</code>

===Merge snapshot and backing file into standalone disk===
<code>
cp test1-base new-master                                 #test1-base = base-disk
qemu-img rebase -b new-master test1-master-0             #snapshot="test1-master-0"
qemu-img commit test1-master-0
qemu-img commit new-master                               #output if success: "Image committed"
Image committed.
qemu-img info new-master
</code> 

===Backup===

<code>
virsh blockcopy --domain kmaster sda \
  /data/images/backup/copy.qcow2 \
  --wait --verbose --shallow \
  --pivot
</code>  
====Pool====

  virsh pool-list --all                                            #show also inactice pool
  virsh pool-list                                                  #show active storage pool
  virsh pool-list --details                                        #show details like disk usage
  virsh pool-info poolname                                         #detailed pool info
  virsh pool-autostart poolame
  virsh pool-start poolname
  virsh pool-undefine poolname                                     #delete pool "default"
  virsh pool-destroy poolname                                      #set inactive
  virsh pool-edit poolname
  virsh pool-define-as --name default --type dir --target /media/work/kvm
  virsh pool-refresh --pool default
  virsh pool-refresh --pool kvm-vm
====Volume====

  virsh vol-list default
  virsh vol-list default --details
  virsh vol-list kvm-vm --details
  virsh vol-delete volume-name.qcow2  --pool default
  virsh vol-create-as default test_vol2.qcow2 2G
  virsh vol-clone --pool default vol1.qcow2 vol2.qcow2
  qemu-img resize volume-name.qcow2 30G && virsh pool-refresh --pool poolname0 #vm has to be shutdown!
  
Pool refesh an volume list:

<code sh pool-vol-ref.sh>
#!/bin/bash

virsh pool-refresh --pool poolname0
virsh pool-refresh --pool poolname1
virsh vol-list poolname0 --details
virsh vol-list poolname1 --details
</code>
  
====clone domain/ vm====

Simple Guest Clone

<code  sh clone-vm.sh>
#!/bin/bash

#author:  Thomas Roehm
#version: 1.0

echo ""
echo "Overview VM´s:"
echo ""
virsh list --all
echo ""
read -p "Please enter the name of the vm you want to clone: " SOURCEVM
echo ""
read -p "Please enter the name of the cloned vm: " DESTVM
echo ""

virt-clone \
--original $SOURCEVM \
--auto-clone \
--name $DESTVM

STATUS=$(echo $?)

echo ""

if [ $STATUS -eq 0 ]
then
        echo "VM \"$DESTVM\" cloned."
else
        echo "Problem - VM not cloned!"
fi
</code>  

====Log====

  journalctl -a -b -k -u libvirtd.service
  systemctl status libvirtd.service

====Link====

https://computingforgeeks.com/virsh-commands-cheatsheet/