KVM

Resource

• KVM Kernel-based Virtual Machine
• https://en.wikipedia.org/wiki/Kernel-based_Virtual_Machine
• Virtual Machine Manager - virt-manager. It can display VNC or SPICE, and uses libvirt to lookup the graphical connection details.
  • How To Manage KVM Virtual Machines With Virt-Manager
  • How to Access Linux Virtual Machines Remotely Over VNC
  • How to Connect to Your VM Over VNC
• My notes:
  • One advantage over VB for me: No need to go to VirtualBox website for the installation and frequent updates. I can use the command line to install it.
  • The desktop screen resolution can be automatically adjusted without a need to install guest addition or vmware tool. Tested Ubuntu and Pop_OS.
  • It has two windows. One is virt-manager and the other is the virtual machine.
  • Use Left Control + Left Alt to escape the virtual machine.
• https://en.wikipedia.org/wiki/QEMU
• It is probably the most widely deployed open source hypervisor in an open source environment.
• KVM cannot be installed on a Windows system.
• How to Install Linux KVM and Create Guest VM with Examples. Para-virtualization, checking the virtualization support on hardware and others. It includes the usage of virsh and virt-install commands.
• Virtualization solutions on Linux systems - KVM and VirtualBox
• Guest additions: it seems QEUM/KVM does not have that to download.
  • Share clipboard. How can I copy&paste from the host to a KVM guest? sudo apt install spice-vdagent in the guest virtual machine. had to reboot guest to be able to make it work. It works.
  • Display resolution. The display has a resolution 1024x768. In the virtual machine window, I do 'View' -> 'Scale to Display' where I choose 'Always' and check the checkbox 'Auto resize VM with window'. It did increase the resolution. See also the command line method: How to increase the visualized screen resolution on QEMU / KVM?
  • Share files
    • QEMU/KVM on Ubuntu and sharing files between host and guests. It works. Modify/create a file /etc/rc.local file to automount the folder at each login. Note the share folder still belongs to the user's group. So we can actually create a soft link for this folder on the host.
    • Is there something like “VirtualBox Guest Additions” for QEMU/KVM?
  • Mouse integration. virt-manager KVM mouse pointer integration (client mouse mode) with Ubuntu guest. Any way to release focus on a KVM guest in virt-manager without having to click Ctrl_L + Alt_L?

• Monitoring performance in virtual machine manager from redhat.com
• How To Use QEMU To Test Operating Systems & Distributions
• Using KVM and VirtualBox side by side and VirtualBox and KVM beside each other
• Comparison
  • Different types of virtualization technologies
  • Pros and cons of QEMU, VMware and VirtualBox
• Fundamental question:
  • Can we install KVM without any Operating System installed -Yes because KVM is already a part of Linux kernel. The Linux kernel acts as the virtualization engine.
  • Is it possible to install the Linux kernel alone?

• Change amount of Ram and CPU cores in KVM, HowTo Add Memory in KVM Virtual Machine

  virsh --version
  virsh list
  virsh dominfo ubuntu16.04 | grep mem
  
  virsh setmaxmem ubuntu16.04 --size 4194304 --config # in KB
  virsh setmem ubuntu16.04 --size 2097152 --config    # in KB
  virsh dominfo ubuntu16.04 | grep mem
  
  # Or edit the XML configuration file
  virsh edit ubuntu16.04
  

libvirt

• https://en.wikipedia.org/wiki/Libvirt. libvirt is an open-source API, daemon and management tool for managing platform virtualization.[3] It can be used to manage KVM, Xen, VMware ESXi, QEMU and other virtualization technologies.
• https://libvirt.org/
• Check libvirt version: sudo head -n2 /var/log/libvirt/qemu/ubuntu2004.log # on Ubuntu 20.04 it shows 6.0.0

Install

Install on Ubuntu

• https://help.ubuntu.com/community/KVM

• Virtualization - The Debian Administrator's Handbook
• How to install KVM on Ubuntu 14.04 LTS Headless Server from cyberciti
• Simple Virtualization With Ubuntu 16.04 Linux and KVM from linuxconfig
• KVM virtualization on a home PC with Linux Mint
• How to Install and Configure KVM on Ubuntu 18.04 LTS Server. I skip step 4: Configure Network Bridge for KVM virtual Machines.
• How to bring down br0 and delete it? After some messing up I need to delete br0.

  sudo ip link set br0 down
  sudo brctl delbr br0
  

• Ubuntu 20.04 Essentials (book) → Creating an Ubuntu 20.04 KVM Networked Bridge Interface. It is based on a Ubuntu Desktop environment. The description is quite detailed. Have not tried yet!
• How to Install KVM on Ubuntu 20.04

  sudo apt install -y qemu qemu-kvm libvirt-daemon \
           libvirt-clients bridge-utils virt-manager
  sudo systemctl status libvirtd
  # enable it to start on boot 
  sudo systemctl enable --now libvirtd
  lsmod | grep -i kvm
  ip a
  # I got two new: virbr0, virbr0-nic
  # Click the superkey (Windows) and search/launch "Virtual Machine Manager"
  

  Click the "Create a new virtual machine" button will result in an error: No active connection to install on. Rebooting does not help. But when I use the command line to create a new VM it works.

  sudo virt-install --name=ubuntu2004 \
    --os-type=Linux \
    --os-variant=ubuntu20.04 \
    --vcpu=2 --ram=2048 \
    --graphics vnc \
    --location=ubuntu-20.04.1-desktop-amd64.iso
  

  Add --network bridge:br0 if we have added a new bridge network (br0) in the host (eg using netplan or nmcli or nm-connection-editor GUI Tool in Ubuntu). See some resource below.

• How to install KVM on Ubuntu 20.04 LTS Headless Server.
  • IP 192.168.2.25 is the new static IP for the bridge network and 192.168.2.254 is the gateway current ethernet is using.
  • Note according to How to add network bridge with nmcli (NetworkManager) on Linux, WiFi is not possible. It only works with Ethernet. Confirmed! The bridge network can be pinged from another computer.
  • How to create wireless bridge connection with nmcli. Ans: This is not possible.
  • I follow this How to add network bridge with nmcli (NetworkManager) on Linux disable STP, turn off “Wired connection 1” and turn on br0.
  • Question: Do I need to turn off "Wired connection 1". It will lose the original host's static IP. The new bridge IP will become the host's IP. The guest machine still obtain a new IP via DHCP. This is not what I expect?
  • Before turn off “Wired connection 1” and turn on br0:

    $ nmcli connection show --active
    NAME                UUID   TYPE      DEVICE  
    Wired connection 1  XXX    ethernet  eno1    
    docker0             XXX    bridge    docker0 
    virbr0              XXX    bridge    virbr0 
    

  • After turn off “Wired connection 1” and turn on br0:

    $ nmcli connection show --active
    NAME               UUID   TYPE      DEVICE  
    br0                xxx    bridge    br0     
    docker0            XXX    bridge    docker0 
    virbr0             XXX    bridge    virbr0  
    bridge-slave-eno1  XXX    ethernet  eno1    
    vnet0              XXX    tun       vnet0 
    

  • I am not able to use remmina to VNC to the bridge VM. Not sure if this is because my host OS is a desktop (not headless).

• Where are image files saved: /var/lib/libvirt/images (/var/lib/docker for Docker)
  • How to move /var directory to another partition
• Troubleshooting: virt-manager can't connect to libvirt. Rebooting computer!

Install qemu-system-arm in Ubuntu

• sudo apt install qemu-system-arm

• How to emulate Raspberry Pi in QEMU which is based on qemu-rpi-kernel-Qemu kernel for emulating Rpi on QEMU.

  mkdir rpi-vm && cd rpi-vm
  git clone https://github.com/dhruvvyas90/qemu-rpi-kernel.git
  
  # Download Raspbian Buster Lite
  # from https://www.raspberrypi.org/downloads/raspberry-pi-os/
  dd if=/dev/zero bs=1M count=4096 >> 2020-08-20-raspios-buster-armhf-lite.img
  
  sudo losetup -f -P --show 2020-08-20-raspios-buster-armhf-lite.img
  
  sudo mount -o rw /dev/loopXp2 /mnt
  
  sudo nano /mnt/etc/fstab
  
  sudo nano /etc/ld.so.preload # Comment out the line and save the file. 
  # Then unmount with the following commands:
  # sudo umount /mnt
  # sudo losetup -d /dev/loopX
  
  qemu-system-arm \
    -M versatilepb \
    -cpu arm1176 \
    -m 256 \
    -kernel qemu-rpi-kernel/kernel-qemu-4.19.50-buster \
    -hda 2020-08-20-raspios-buster-armhf-lite.img \
    -append "dwc_otg.lpm_enable=0 root=/dev/sda2 console=tty1 rootfstype=ext4 elevator=deadline rootwait" \
    -dtb qemu-rpi-kernel/versatile-pb-buster.dtb \
    -no-reboot \
    -serial stdio
  
  # We can install a desktop. See 
  # https://www.raspberrypi.org/forums/viewtopic.php?t=133691
  

Install on CentOS

• How to install KVM on CentOS 8 Headless Server
• How to install KVM on CentOS 7 / RHEL 7 Headless Server
• How to Deploy Multiple Virtual Machines using Network Install (HTTP, FTP and NFS) under KVM Environment

snapshot

• How to Create, Revert and Delete KVM Virtual machine (domain) snapshot with virsh command, How to create snapshot in Linux KVM VM/Domain

  $ sudo su
  # virsh list --all
  
  # virsh snapshot-create-as --domain win10 --name win10_snap --description "Windows 10 snapshot"    # Create a snapshot
  # virsh snapshot-list win10
  # virsh snapshot-info --domain win10 --snapshotname win10_snap
  
  # virsh snapshot-revert win10 win10_snap    # Restore
  
  # virsh snapshot-delete --domain win10 --snapshotname win10_snap
  

• To create a snapshot using the GUI, open virtualization manager window. In the VM properties, click on the icon (two displays overlapped) which is on the right of the menu, which says Manage VM snapshots.

GUI manager

• Manage KVM Virtual Machines Using Cockpit Web Console
• How To Manage KVM Virtual Machines With Virt-Manager. View -> Graph -> Memory Usage

Network

• Host only (used by VirtualBox) = Isolated network (used by KVM). Step 1: Select a VM. Click Edit, choose "Connection Details" and add a new network (Isolated mode). This default network has IPv4 192.168.122.0/24 Step 2: Click Edit, choose "Virtual machine Details" and click the Information icon (circle shape). Click "Add Hardware" and choose "Isolated network" for the Network source. Leave the MAC address and Device model as defaults. This network network has IP4 192.168.100.0/24.
• How to Configure Network Bridge in Ubuntu*. Three methods. Excellent instruction!
  • The new (slave-type) bridge network should tie to one of existing network adapters for this to work.
  • The new adapter will be br0 only if we use the netplan method.
  • If we use the nmcli or the nm-connection-editor GUI method, we need to deactivate the Ethernet interface (if we use Ethernet). The final adapters will have br0 and bridge-br0.
  • To set a static IP on the host, see Ubuntu -> Set static IP, How to Configure Static IP Address on Ubuntu 20.04.
• How to configure bridged network in virt-manager (CentOS / RHEL 7)
• Install And Set Up KVM On Ubuntu 20.04 Focal Fossa Linux
• KVM: Creating a bridged network with NetPlan on Ubuntu bionic
• VirtualNetworking
• Network XML format
• KVM Networking - NAT & Host-Only
• Home Lab Project: Network Bridges for KVM - NAT, Host-only, Isolated

Back and restore images

How to KVM Backup and Restore in Linux

# Backup 
virsh list --all
virsh dumpxml win10 > /MyBackup/win10.xml
sudo cp /var/lib/libvirt/images/win10.qcow2 /MyBackup/win10.qcow2
sudo chown $USER:$USER /MyBackup/*.qcow2

# Restore Making
sudo virsh undefine win10
ls -l /etc/libvirt/qemu
virsh list --all
sudo rm /var/lib/libvirt/images/win10.qcow2
sudo cp /MyBackup/win10.qcow2 /var/lib/libvirt/images/
sudo virsh define --file /MyBackup/win10.xml
# virsh start win10

Cheat sheet

KVM Cheatsheet

Run macOS on KVM / QEMU

How To run macOS on KVM / QEMU