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Getting Started with Kernel-based Virtual Machine (KVM)
Presentation slides for Getting Started with Kernel-based Virtual Machine (KVM) workshop at Open Source Summit Europe 2022.
**[Getting Started with Kernel-based Virtual Machine (KVM)](https://osseu2022.sched.com/event/15z24)** / [Open Source On-Ramp](https://osseu2022.sched.com/overview/type/Open+Source+On-Ramp) / **[Open Source Summit Europe 2022](https://osseu2022.sched.com/)**
Leonard Sheng Sheng Lee
[Leonard Sheng Sheng Lee](https://github.com/sheeeng) / Made with [Marp](https://marp.app/) / Participants Agree to Abide by [Code of Conduct](https://events.linuxfoundation.org/open-source-summit-europe/attend/code-of-conduct/)
linux,kvm,virtualization,marp,marp-cli,slide
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Getting Started with Kernel-based Virtual Machine (KVM)

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Abstract (Part 1/5)

  • Want to get started with Kernel-based Virtual Machine (KVM)?
  • Want to run a virtual machine on your system using open source technologies?
  • Want to interact with KVM virtual machines from command line interface (CLI)?

Abstract (Part 2/5)

In this tutorial, Leonard will be teaching people to familiarize themselves with KVM technologies, which allows virtual machines to run with near native performance.

Abstract (Part 3/5)

Participants must have a basic knowledge of how the Linux operating system works, and must have a recent Linux based operating system running on a portable computer to join this tutorial.

Abstract (Part 4/5)

We will be focusing on tasks such as creating, accessing, modifying, and deleting KVMs, primarily using CLI and if time permits, using a graphical user interface (GUI) too.

Abstract (Part 5/5)

At the end of this tutorial, participants are expected to know how to check if KVM is supported on their computer hardware and manage KVMs with confidence.

Agenda / Tasks / 90 Minutes

  • Setup Kernel-based Virtual Machine (KVM)
  • Manage KVM Using:
    • Command Line Interface (CLI)
    • Graphical User Interface (GUI)*

$_{*If\ time\ permits.}$

🙋‍♂️ 🙋 🙋‍♀️

Overview of Kernel-based Virtual Machine (KVM) (Part 1/2)

  • An open source virtualization technology built into Linux®. Turn Linux into a hypervisor.
  • Allows a host machine to run multiple, isolated virtual environments called guests or virtual machines (VMs).
  • Available from Linux 2.6.20 or newer.

Overview of Kernel-based Virtual Machine (KVM) (Part 2/2)

  • KVM converts Linux into a type-1 (bare-metal) hypervisor.
  • Every VM is implemented as a regular Linux process, scheduled by the standard Linux scheduler, with dedicated virtual hardware components.

Overview of Hypervisor

  • A hypervisor is software that creates and runs virtual machines (VMs).
  • It is also called a virtual machine monitor (VMM).
  • It isolates the hypervisor operating system and resources from the virtual machines and enables the creation and management of those VMs.

Overview of QEMU (Quick Emulator)

  • QEMU (Quick Emulator) is part of the KVM experience being the userspace backend for it, but it also can be used for hardware without virtualization extensions by using its Tiny Code Generator (TCG) mode.

Why Virtual Machines Called Domain? (Part 1/2)

  • Domain0 is the first domain started by the hypervisor at boot, and will be running a Linux OS. This domain is privileged: it may access the hardware and can run the tools that manage other domains.

Why Virtual Machines Called Domain? (Part 2/2)

  • These other domains are referred to as DomUs with the U standing for "user". They are unprivileged, and the equivalent to a guest system or guest virtual machine.

Task 1

Setup Kernel-based Virtual Machine (KVM)

Hardware Virtualization Support (Part 1/2)

  • KVM requires a CPU with virtualization extensions.
    • Intel® Virtualization Technology (Intel® VT)
      • CPU flag is vmx (Virtual Machine Extensions).
    • AMD virtualization (AMD-V)
      • CPU flag is svm (Secure Virtual Machine).

Hardware Virtualization Support (Part 2/2)

egrep --count '^flags.*(vmx|svm)' /proc/cpuinfo
  • If output is 0, your system does not support the relevant virtualization extensions or disabled on BIOS. You can still use QEMU/KVM, but the emulator will fall back to software virtualization, which is much slower.

Installing Virtualization Packages (Fedora)

dnf groupinfo virtualization

dnf group install \
    virtualization \
    --with-optional \
    --assumeyes

Installing Virtualization Packages (Ubuntu)

# apt-get install \
    bridge-utils \
    qemu-kvm \
    virt-manager

Installing Virtualization Packages (CentOS)

# yum install \
    libvirt \
    qemu-kvm \
    virt-install \
    virt-install \
    virt-manager

Enable libvirtd Service

  • The libvirtd service is a server side daemon and driver required to manage the virtualization capabilities of the KVM hypervisor.

  • Start libvirtd service and enable it on boot.

systemctl start libvirtd

systemctl enable libvirtd

Verify KVM Kernel Modules

  • Verify that the KVM kernel modules are properly loaded.
lsmod | egrep 'kvm_*(amd|intel)'
  • If output contains kvm_intel or kvm_amd, KVM is properly configured.

Append Groups to Manage KVM

  • Append current user to kvm and libvirt groups to create and manage virtual machines.
usermod --append --groups=kvm,libvirt ${USER}

cat /etc/group | egrep "^(kvm|libvirt).*${USER}"
  • Log out and log in again to apply this modification.

Update QEMU Configuration

# cp /etc/libvirt/qemu.conf /etc/libvirt/qemu.conf.original
# sed --in-place \
    "s,\#user = \"root\",\#user = \"${USER}\",g" \
    /etc/libvirt/qemu.conf
# sed --in-place \
    "s,\#group = \"root\",\#group = \"libvirt\",g" \
    /etc/libvirt/qemu.conf
# diff --unified \
    /etc/libvirt/qemu.conf.original \
    /etc/libvirt/qemu.conf
systemctl restart libvirtd

Task 2

Manage KVM using Command Line Interface (CLI)

Install Debian from Network

$ virt-install \
    --name Debian11 --os-variant debian11 --description 'Debian11' \
    --vcpus 2 --ram 2048 \
    --location \
    https://ftp.debian.org/debian/dists/stable/main/installer-amd64 \
    --network bridge=virbr0 \
    --graphics vnc,listen=127.0.0.1,port=5901 \
    --noreboot --noautoconsole \
    --extra-args 'console=ttyS0,115200n8 serial'
$ virt-viewer --connect qemu:///session --wait Debian11

View Serial Console Message

$ virsh console Debian11
Connected to domain 'Debian11'
Escape character is ^] (Ctrl + ])

Guest Virtual Machine States and Types (Part 1/2)

Several virsh commands are affected by the type of the guest virtual machine: ‎ Transient or Persistent.

Guest Virtual Machine States and Types (Part 2/2)

During the life cycle of a virtual machine, libvirt will classify the guest as any of the following states: ‎ Undefined, Shut off, Running, Paused, Saved

Display virsh Version

virsh version virsh version --daemon

Connect to Hypervisor (Part 1/2)

virsh connect [hostname-or-URI] [--readonly] ‎ The most commonly used URIs are: qemu:///system, qemu:///session, lxc:///

Connect to Hypervisor (Part 2/2)

For example, establish a session to connect to your set of guest virtual machines (VMs), with you as the local user: ‎ virsh connect qemu:///session

List Guest VM Connected to Hypervisor

virsh list --all virsh list --inactive

Display Information about Hypervisor

virsh hostname virsh sysinfo

Take Screenshot of Virtual Machine

virsh screenshot $<Domain-{Id,Name,Uuid}> [imagefilepath] [--screen screenID] ‎ Example: virsh screenshot Debian11

Extra: Start Guest Virtual Machine

virsh start $<Domain-{Id,Name,Uuid}> [--console] [--paused] [--autodestroy] [--bypass-cache] [--force-boot] ‎ Starts the $<Domain-{Id,Name,Uuid}> that you already created and is currently in the inactive state.

Configuring a Virtual Machine to be Started Automatically at Boot

virsh autostart [--disable] $<Domain-{Id,Name,Uuid}> ‎ Example: virsh autostart Debian11

Extra: Rebooting a Guest Virtual Machine

virsh reboot $<Domain-{Id,Name,Uuid}> [--mode <RebootModeName>] ‎ Example: virsh reboot Debian11 --mode initctl

Extra: Save Guest Virtual Machine's Configuration

virsh save [--bypass-cache] domain file [--xml string] [--running] [--paused] [--verbose] ‎ Example: virsh save Debian11 Debian11-Configuration.xml --running

Extra: Define Guest VM with XML File

virsh define $<Domain-{Id,Name,Uuid}>.xml ‎ Example: virsh define Debian11-Configuration.xml

Extra: Extract Guest VM XML File

virsh save-image-dumpxml file --security-info ‎ Example: virsh save-image-dumpxml Debian11-Configuration.xml

Extra: Edit Guest VM Configuration

virsh save-image-edit <file> [--running] [--paused] ‎ Example: virsh save-image-edit Debian11-Configuration.xml --running

Extra: Restore Guest Virtual Machine

virsh restore <file> [--bypass-cache] [--xml /path/to/file] [--running] [--paused] ‎ Example: virsh restore Debian11-Configuration.xml --running

Extra: Resuming a Guest Virtual Machine

virsh resume $<Domain-{Id,Name,Uuid}>

Display Host Physical Machine Name

virsh domhostname $<Domain-{Id,Name,Uuid}>

Display Guest VM General Information

virsh dominfo $<Domain-{Id,Name,Uuid}>d/Domain-Name/Uuid}

Display Guest VM's ID Number

virsh domid $<Domain-{Id,Name,Uuid}>

Extra: Abort Running Jobs on a Guest VM

virsh domjobabort $<Domain-{Id,Name,Uuid}>

List Statistic about Guest VM

virsh domjobinfo $<Domain-{Id,Name,Uuid}>

Display Guest Virtual Machine's Name

virsh domname $<Domain-{Id,Uuid}>

Display Virtual Machine's State

virsh domstate $<Domain-{Id,Name,Uuid}>

Display Connection State to the Virtual Machine

virsh domcontrol $<Domain-{Id,Name,Uuid}>

Shut Down Guest Virtual Machine

virsh shutdown $<Domain-{Id,Name,Uuid}> [--mode modename] ‎ Example: virsh shutdown Debian11 --mode acpi

Suspend Guest Virtual Machine

virsh suspend $<Domain-{Id,Name,Uuid}> ‎ Example: virsh suspend Debian11

Reset Virtual Machine

virsh reset $<Domain-{Id,Name,Uuid}> ‎ Example: virsh reset Debian11

Stop Running Guest Virtual Machine To Restart It Later

virsh managedsave $<Domain-{Id,Name,Uuid}> --bypass-cache --running | --paused | --verbose ‎ Example: virsh managedsave Debian11 --running

Extra: Listing, Creating, Applying, and Deleting a Snapshot

qemu-img snapshot [ -l | -a snapshot | -c snapshot | -d snapshot ] filename

Remove and Delete a Virtual Machine

virsh undefine $<Domain-{Id,Name,Uuid}> [--managed-save] [storage] [--remove-all-storage] [--wipe-storage] [--snapshots-metadata] [--nvram] ‎ Example: virsh undefine Debian11 --remove-all-storage

Force a Guest Virtual Machine to Stop

virsh destroy $<Domain-{Id,Name,Uuid}> ‎ Example: virsh undefine Debian11 --remove-all-storage

Virtual Machine Termination

$ virsh shutdown Debian11 # Graceful Shutdown
Domain 'Debian11' is being shutdown

$ virsh destroy Debian11 # Force Shutdown
Domain 'Debian11' destroyed

$ virsh undefine Debian11
Domain 'Debian11' has been undefined

Extra: Related Commands

$ virsh nodeinfo
$ virsh edit

$ virt-df
$ virt-top
$ virt-viewer

$ virsh pool-list --all
$ virsh pool-destroy
$ virsh pool-undefine

Extra: List OS Variant

virt-install --os-variant list

Extra: Install Ubuntu from ISO Image

$ virt-install \
    --name Ubuntu --os-variant ubuntu22.04 --description 'Ubuntu' \
    --vcpus 2 --ram 2048 \
    --network bridge=virbr0,model=virtio \
    --graphics vnc,listen=127.0.0.1,port=5902 \
    --cdrom ~/Downloads/ubuntu-22.04-desktop-amd64.iso \
    --noreboot --noautoconsole
$ virt-viewer --connect qemu:///session --wait Ubuntu

Extra: Install Ubuntu from Network

$ virt-install \
    --name Ubuntu --os-variant ubuntu20.04 --description 'Ubuntu' \
    --vcpus 2 --ram 2048 \
    --location \
    http://archive.ubuntu.com/ubuntu/dists/focal/main/installer-amd64/ \
    --network bridge=virbr0,model=virtio \
    --graphics vnc,listen=127.0.0.1,port=5902 \
    --noreboot --noautoconsole \
    --extra-args='console=ttyS0,115200n8 serial edd=off'
$ virt-viewer --connect qemu:///session --wait Ubuntu
$ virsh console Ubuntu

Extra: Install Fedora from ISO Image

$ virt-install \
    --name Fedora --os-variant fedora36 --description 'Fedora' \
    --vcpus 2 --ram 2048 \
    --network bridge=virbr0,model=virtio \
    --graphics vnc,listen=127.0.0.1,port=5904 \
    --cdrom ~/Downloads/Fedora-Workstation-Live-x86_64-36-1.5.iso \
    --noreboot --noautoconsole
$ virt-viewer --connect qemu:///session --wait Fedora

Extra: Install Fedora from Network

$ virt-install \
    --name Fedora --os-variant fedora36 --description 'Fedora' \
    --vcpus 2 --ram 2048 \
    --location \
    https://download.fedoraproject.org/pub/fedora/linux/releases/36/Server/x86_64/os \
    --network bridge=virbr0,model=virtio \
    --graphics vnc,listen=127.0.0.1,port=5904 \
    --noreboot \
    --extra-args='console=ttyS0,115200n8 edd=off'
$ virsh console Fedora

Extra: Install AlmaLinux from ISO Image

$ virt-install \
    --name AlmaLinux --os-variant almalinux9 --description 'AlmaLinux' \
    --vcpus 2 --ram 3072 \
    --network bridge=virbr0,model=virtio \
    --graphics vnc,listen=127.0.0.1,port=5903 \
    --cdrom ~/Downloads/AlmaLinux-9.0-x86_64-dvd.iso \
    --noreboot --noautoconsole
$ virt-viewer --connect qemu:///session --wait AlmaLinux

Extra: Install AlmaLinux from Network

$ virt-install \
    --name AlmaLinux --os-variant almalinux9 --description 'AlmaLinux' \
    --vcpus 2 --ram 3072 \
    --location \
    https://almalinux.uib.no/9.0/BaseOS/x86_64/os/ \
    --network bridge=virbr0,model=virtio \
    --graphics vnc,listen=127.0.0.1,port=5905 \
    --noreboot \
    --extra-args='console=ttyS0,115200n8 edd=off'
$ virsh console AlmaLinux

Extra: Install CentOS from ISO Image

$ virt-install \
    --name CentOS --os-variant centos-stream9 --description 'CentOS' \
    --vcpus 2 --ram 3072 \
    --network bridge=virbr0,model=virtio \
    --graphics vnc,listen=127.0.0.1,port=5902 \
    --cdrom ~/Downloads/CentOS-Stream-9-latest-x86_64-dvd1.iso \
    --noreboot --noautoconsole
$ virt-viewer --connect qemu:///session --wait CentOS

Extra: Install CentOS from Network

$ virt-install \
    --name CentOS --os-variant centos-stream9 --description 'CentOS' \
    --vcpus 2 --ram 3072 \
    --location \
    https://mirror.netsite.dk/centos-stream/9-stream/BaseOS/x86_64/os/ \
    --network bridge=virbr0,model=virtio \
    --graphics vnc,listen=127.0.0.1,port=5904 \
    --noreboot \
    --extra-args='console=ttyS0,115200n8 edd=off'
$ virt-viewer --connect qemu:///session --wait CentOS
$ virsh console CentOS

Error: Refusing to Undefine

$ virsh undefine Ubuntu --remove-all-storage
error: Refusing to undefine while domain managed save image exists
$ virsh managedsave-remove Ubuntu
Removed managedsave image for domain 'Ubuntu'
$ virsh undefine Ubuntu
Domain 'Ubuntu' has been undefined

Error: Failed to Get MTU of Bridge

stderr=failed to get mtu of bridge `virbr0': No such device

# systemctl restart libvirtd
$ brctl show
bridge name	bridge id		STP enabled	interfaces
virbr0		8000.525400a87247	yes

Error: Hangs on Probing EDD

Booting from Hard disk....
Probing EDD (edd=off to disable)... ok

$ virt-install \
    ...
    --extra-args='... edd=off'

Error: Failed to Get Domain

  • Ensure that specified storage pool has correct permissions and path.
$ virsh pool-list --all
$ virsh pool-info default
$ virsh pool-dumpxml default
$ virsh pool-dumpxml default \
    | xmlstarlet sel --template --copy-of "/pool/target"
$ virsh pool-dumpxml default \
    | xmlstarlet sel --template --value-of "/pool/target/path"

Error: Cannot Access Storage File (UID:107, GID:107)

# cp /etc/libvirt/qemu.conf /etc/libvirt/qemu.conf.original
# sed --in-place \
    "s,\#user = \"root\",\#user = \"${USER}\",g" \
    /etc/libvirt/qemu.conf
# sed --in-place \
    "s,\#group = \"root\",\#group = \"libvirt\",g" \
    /etc/libvirt/qemu.conf
# systemctl restart libvirtd

Error: Missing 'Default' Network?

$ virsh net-list --all
 Name   State   Autostart   Persistent
----------------------------------------

$ sudo virsh net-list --all
 Name      State    Autostart   Persistent
--------------------------------------------
 default   active   yes         yes

Read this post if default network is still missing.

Task 3

Manage KVM using Graphical User Interface (GUI)* $_{(*if\ time\ permits)}$

Use virt-manager to create, manage, & delete KVMs.

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Bonus: Unattended Install

Bonus: Assign Host USB Device

https://www.linux-kvm.org/page/USB_Host_Device_Assigned_to_Guest

🙏

End