Using QEMU on Ubuntu
What is QEMU?
QEMU is a generic and open source machine emulator and virtualizer.
source: https://www.qemu.org/
Install a Virtual Machine Manager GUI for KVM
sudo apt-get install virt-manager
https://www.ubuntubuzz.com/2016/05/how-to-install-kvm-with-gui-virt-manager-in-ubuntu.html
How To Install Ubuntu in QEMU/KVM Virtual Machine
https://www.ubuntubuzz.com/2016/05/how-to-install-ubuntu-in-qemukvm-virtual-machine.html
What is QCOW2?
QCOW2 is a storage format for virtual disks. QCOW stands for QEMU copy-on-write. The QCOW2 format decouples the physical storage layer from the virtual layer by adding a mapping between logical and physical blocks. Each logical block is mapped to its physical offset, which enables storage over-commitment and virtual machine snapshots, where each QCOW volume only represents changes made to an underlying virtual disk.
The initial mapping points all logical blocks to the offsets in the backing file or volume. When a virtual machine writes data to a QCOW2 volume after a snapshot, the relevant block is read from the backing volume, modified with the new information and written into a new snapshot QCOW2 volume. Then the map is updated to point to the new place.
source: https://access.redhat.com/solutions/641193
from: Kernel Recipes 2015 - Speed up your kernel development cycle with QEMU - Stefan Hajnoczi
How to boot a development kernel
qemu-system-x86_64 -enable-kvm -m 1024 \
-kernel /boot/vmlinuz \
-initrd /boot/initrd.img \
-append 'console=ttyS0' \
-nographic
-m 1024 means 1GB RAM
In the video, initramfs.img is used, but on my machine it’s initrd.img
This text showed after running the commmand above:
No root device specified. Boot arguments must include a root= parameter.
Some things that may solve it, but I didn’t investigate it further yet …:
Unable to run linux kernel image on qemu
Build process
Compile your kernel modules:
make M=drivers/virtio \
CONIG_VIRTIO_PCI=m modules
Build initramfs:
usr/gen_init_cpio input | gzip >initramfs.img
Run virtual machine:
qemu-system-x86_64 -m 1024 -enable-kvm \
-kernel arch/x86_64/boot/bzImage \
-initrd initramfs.img \
-append 'console=ttyS0' \
-nographic
initramfs vs initrd
The difference between initrd and initramfs?
How to use custom image kernel for ubuntu in qemu?
https://stackoverflow.com/questions/65951475/how-to-use-custom-image-kernel-for-ubuntu-in-qemu
References
https://www.qemu.org/download/
https://qemu-project.gitlab.io/qemu/
https://wiki.qemu.org/Documentation
https://gitlab.com/qemu-project/qemu/-/tree/master/docs