How to install Ubuntu 23.04 in Qemu/KVM on Ubuntu Host

Qemu(+KVM) is a powerful virtualization solution for linux oses. KVM (Kernel based Virtual Machine) is a module built into the linux kernel that provides it virtualization capabilities. Qemu is a hardware emulator that uses kvm to provides all necessary features to create and launch virtual machines with guest operating systems.

The other more commonly used virtualization solution is virtualbox which is an all gui solution and allows to easily create and manage virtual machine and supports all major operating systems as guest.

However, Qemu+KVM has a much smaller footprint and is lightweight compared to virtualbox without much compromise on features.

In a previous post we saw how to boot Ubuntu live iso with Qemu: How to Boot Ubuntu 23.04 Live ISO with Qemu/KVM on Ubuntu Host

In this article we shall take a look at how to create a virtual disk using qemu and then install Ubuntu as guest os in it. In our current setup we are using Kubuntu 23.04 as the host os and Ubuntu 23.04 will be installed as the guest os.

Qemu Version on our host system:

$ qemu-system-x86_64 -version
QEMU emulator version 7.2.0 (Debian 1:7.2+dfsg-5ubuntu2)
Copyright (c) 2003-2022 Fabrice Bellard and the QEMU Project developers
enlightened@enlightened:~$

Create Virtual Disk

The first step is to create a virtual disk, where the guest os will be installed. The file format of the virtual disk is is "qcow" (Qemu copy-on-write v2). The qemu-img command is used like this:

qemu-img create -f qcow2 ubuntu2304.qcow 20G

It takes only a few seconds to finish.

$ qemu-img create -f qcow2 ubuntu2304.qcow 20G
Formatting 'ubuntu2304.qcow', fmt=qcow2 cluster_size=65536 extended_l2=off compression_type=zlib size=21474836480 lazy_refcounts=off refcount_bits=16
$

Boot ISO with virtual disk attached

Boot with the cdrom iso and the virtual disk attached. So that we can install from the live boot session. Here is the command

qemu-system-x86_64 --enable-kvm -cpu host -smp 4 -m 4096 -device virtio-vga -boot d -cdrom ubuntu-23.04-desktop-amd64.iso -drive file=ubuntu2304.qcow,format=qcow2

Before installation check that your virtual disk is being seen by qemu. In the live ubuntu guest session run the lsblk command as shown below. Note the 20G ATA sda drive which we just created using the qemu-img command.

ubuntu@ubuntu:~$ lsblk -e7 -o "NAME,PTTYPE,FSTYPE,SIZE,LABEL,PARTLABEL,PATH,PHY-SEC,VENDOR"
NAME PTTYPE FSTYPE   SIZE LABEL              PARTLABEL PATH     PHY-SEC VENDOR
fd0                    4K                              /dev/fd0     512 
sda                   20G                              /dev/sda     512 ATA     
sr0  PMBR   iso9660  4.6G Ubuntu 23.04 amd64           /dev/sr0    2048 QEMU    
ubuntu@ubuntu:~$

The 20G sda virtual disk is where the ubuntu guest shall be installed.

Run the Installation

Now click on Install Ubuntu and follow the process to install Ubuntu as you would normally do on any desktop. We shall not be elaborating this part in much detail, and expect you to know what to do and how.

Once the installation process is complete, shutdown the system.

Boot into installed Guest

Now we can finally boot into the installed guest using the virtual disk file. Note that we shall not be attaching the cdrom iso anymore as we don't need it after the installation is complete.

qemu-system-x86_64 --enable-kvm -cpu host -smp 4 -m 4096 -vga virtio -boot c -drive file=ubuntu2304.qcow,format=qcow2

If all goes fine you should be presented with the Ubuntu desktop ready for work.

Check configurations

Once we have booted installed ubuntu we can check couple of things to understand how the qemu system is setup and configured.

Checking the file systems: We can check the file systems in use with the df command. The output shows that about 10GB out of the 20GB space has been used by ubuntu for installation.

silver@silverqemukvm:~$ df -h
Filesystem      Size  Used Avail Use% Mounted on
tmpfs           390M  1.5M  389M   1% /run
/dev/sda2        20G  9.9G  8.7G  54% /
tmpfs           2.0G     0  2.0G   0% /dev/shm
tmpfs           5.0M     0  5.0M   0% /run/lock
tmpfs           390M  168K  390M   1% /run/user/1000
silver@silverqemukvm:~$

PCI Devices: Check the output of lspci for emulated hardware details.

silver@silverqemukvm:~$ lspci
00:00.0 Host bridge: Intel Corporation 440FX - 82441FX PMC [Natoma] (rev 02)
00:01.0 ISA bridge: Intel Corporation 82371SB PIIX3 ISA [Natoma/Triton II]
00:01.1 IDE interface: Intel Corporation 82371SB PIIX3 IDE [Natoma/Triton II]
00:01.3 Bridge: Intel Corporation 82371AB/EB/MB PIIX4 ACPI (rev 03)
00:02.0 Ethernet controller: Intel Corporation 82540EM Gigabit Ethernet Controller (rev 03)
00:03.0 VGA compatible controller: Red Hat, Inc. Virtio GPU (rev 01)
silver@silverqemukvm:~$

Video Device (VGA)

silver@silverqemukvm:~$ lspci -vnn | grep -i vga -A 12
00:03.0 VGA compatible controller [0300]: Red Hat, Inc. Virtio GPU [1af4:1050] (rev 01) (prog-if 00 [VGA controller])
	Subsystem: Red Hat, Inc. Virtio GPU [1af4:1100]
	Flags: bus master, fast devsel, latency 0, IRQ 11
	Memory at fe000000 (32-bit, prefetchable) [size=8M]
	Memory at fe800000 (64-bit, prefetchable) [size=16K]
	Memory at febb0000 (32-bit, non-prefetchable) [size=4K]
	Expansion ROM at 000c0000 [disabled] [size=128K]
	Capabilities: <access denied>
	Kernel driver in use: virtio-pci

silver@silverqemukvm:~$

Network Configuration: According to ifconfig output the network adapter is in NAT mode, which gives it an ip not on the same subnet as the host or lan router. This makes it difficult to access the device from ssh, unless some other settings are used.

The guest os can access the internet fine, but there is no way for the host os to communicate with the guest os through networking, unless bridge network or port forwarding is configured.

silver@silverqemukvm:~$ ifconfig
ens2: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet 10.0.2.15  netmask 255.255.255.0  broadcast 10.0.2.255
        inet6 fec0::dbed:bcb8:ecb8:4ad6  prefixlen 64  scopeid 0x40<site>
        inet6 fec0::4c0e:69b4:cab2:90e8  prefixlen 64  scopeid 0x40<site>
        inet6 fe80::e0c6:1ce6:e461:81aa  prefixlen 64  scopeid 0x20<link>
        ether 52:54:00:12:34:56  txqueuelen 1000  (Ethernet)
        RX packets 27092  bytes 28884455 (28.8 MB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 12249  bytes 1540180 (1.5 MB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

lo: flags=73<UP,LOOPBACK,RUNNING>  mtu 65536
        inet 127.0.0.1  netmask 255.0.0.0
        inet6 ::1  prefixlen 128  scopeid 0x10<host>
        loop  txqueuelen 1000  (Local Loopback)
        RX packets 1477  bytes 185623 (185.6 KB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 1477  bytes 185623 (185.6 KB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

silver@silverqemukvm:~$

OpenGL: The opengl renderer is Mesa llvmpipe which indicates software based emulation of opengl and no gpu driver available.

silver@silverqemukvm:~$ glxinfo | grep -i opengl
OpenGL vendor string: Mesa
OpenGL renderer string: llvmpipe (LLVM 15.0.7, 256 bits)
OpenGL core profile version string: 4.5 (Core Profile) Mesa 23.0.2
OpenGL core profile shading language version string: 4.50
OpenGL core profile context flags: (none)
OpenGL core profile profile mask: core profile
OpenGL core profile extensions:
OpenGL version string: 4.5 (Compatibility Profile) Mesa 23.0.2
OpenGL shading language version string: 4.50
OpenGL context flags: (none)
OpenGL profile mask: compatibility profile
OpenGL extensions:
OpenGL ES profile version string: OpenGL ES 3.2 Mesa 23.0.2
OpenGL ES profile shading language version string: OpenGL ES GLSL ES 3.20
OpenGL ES profile extensions:
silver@silverqemukvm:~$

Post Installation

After the installation is complete you would need to update all packages first before you can install anything:

sudo apt update && sudo apt dist-upgrade -y

Now you can proceed with installation of needed packages.

Host OS Details

Here are the details of the host os kernel version.

$ lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description:    Ubuntu 23.04
Release:        23.04
Codename:       lunar
$

Kernel version:

$ uname -a
Linux enlightened 6.2.0-20-generic #20-Ubuntu SMP PREEMPT_DYNAMIC Thu Apr  6 07:48:48 UTC 2023 x86_64 x86_64 x86_64 GNU/Linux
$

Conclusion

The qemu supports native resolution for the guest operating system very easily. However other features like shared clipboard, drag and drop are a bit more difficult to get to work. We shall be covering those features in future articles.

In this article we used only command line tools to create and setup the virtual machines. If you want a gui tool look at virt-manager which uses libvirt to create and manage qemu virtual machines and provides an easy user interface similar to virtualbox.