The shape of VM to come

Install a Virtual Machine using qemu

Install qemu

Get qemu
git clone https://gitlab.com/qemu-project/qemu.git

Install qemu

mkdir build \
cd build \
../configure --enable-slirp \
make -j \
sudo make install \

Install a VM using qemu

Get an image of debian12.2.0 we want to boot on as a virtual machine:
wget https://www.debian.org/distrib/netinst/debian-12.2.0-amd64-netinst.iso .

Create a disk image (qcow2 format) where the vm will store
qemu-img create -f format qcow2 mydisk.img 20G

Install the vm running on debian with qemu:

qemu-system-x86_64 -boot d -cdrom debian-12.2.0-amd64-netinst.iso -m 4G \
-device e1000,netdev=net0,mac=52:54:00:12:34:56 -netdev user,id=net0,hostfwd=tcp::10022-:22 \
-hda mydisk.img -accel kvm

Follow all instruction from the interface and you're done. -accel kvm helps boosting the installation time (from 1h30 to 20min in my case)

Launch our new VM

Let's say we want to run debian with 8Gb of ram:
qemu-system-x86_64 -hda mydisk.img -m 8G -accel kvm

A vm can use a lot of ressources and slow down its usage, we can lighten our efforts by disabling all graphical interface: Open a terminal within the vm and run

sudo systemctl set-default multi-user.target
sudo reboot

Just in case, you can re-enable it with:

systemctl set-default graphical.target
sudo reboot