Install kvm on Ubuntu Linux

Check if kvm can run on the computer
$ sudo kvm-ok <enter>

If it returns lines as follows, then it will work
INFO: /dev/kvm exists
KVM acceleration can be used

Install qemu-kvm
Open a terminal window and enter the commands below.
$ sudo apt-get install qemu-kvm libvirt-daemon-system libvirt-clients bridge-utils virt-viewer virt-manager <enter>

$ sudo adduser <user> libvirt <enter>
where user is the user name on the Linux computer.

$ sudo adduser <user> kvm <enter>
where user is the user name on the Linux computer.

Check the status with:
$ sudo systemctl status libvirtd <enter>
$ sudo systemctl enable --now libvirtd <enter>
$ lsmod | grep -i kvm <enter>
$ sudo systemctl status libvirtd <enter>

You can also import VirtualBox hard disk .vdi files.