Simple guide for installing debian12 on qemu.

Requirements:

Your machine should have atleast 8gb of ram.
You should have an unix based operating system installed on your machines.
Stable internet connection.
qemu installed on your machine.

(assuming you have qemu installed on your system if not refer to qemu-wiki here https://www.qemu.org/download/ )

step1:

Download the iso image from the debians server.
ISO
Note: Don't go for the images where there is a gui as they tend be bloated and are slow to run on vm. instead chose the standard debian img without any gui.

step2:

Create a folder with any name you want here we are creating one with name deb:
(this is done in order keep everything together in one folder)
$mkdir deb
$cd deb
Once you are in the folder make the virtual drive on which we will install debian.
$qemu-img create -f qcow2 disk.qcow 32g
- here qemu-img is the utility provided by qemu to make virtual drives in qcow format which again is provided by qemu.
- 'create' tell the utility to create a new disk img,
- '-f' flag specifies the format of the disk image
- 'qcow2' is the format name
- 'disk.qcow' is the name we are giving to the disk
- '32G' will be the max size of the disk we are creating.

step3:

run the command:

$qemu-system-x86_64 -m 4096 -smp 2 -cdrom ../isos/debian-live-12.2.0-amd64-standard.iso -drive if=virtio,file=disk.qcow2,format=qcow2

'-m' flag tell the qemu to start with how much memory
'-smp' sets the number of cores to start with
'-cdrom' selects the booting media or installing media in our the case the iso we downloaded earlier
'-drive' selects the media or drive on where have to install the os.
(press enter assuming you know how to install debian (installing debian is not as easy as just clicking buttons(it might be but anyways)))
when you press return a new window will pop up with debians banner installation page.
after you have successfully gone through all the steps of installing,

step4:

To run your newly made vm run the command

$qemu-system-x86_64 -m 4096 -smp 2 -drive if=virtio,file=disk.qcow2,format=qcow2 -netdev user,id=mynet0,hostfwd=tcp:127.0.0.1:7922-:22 -device virtio-net,netdev=mynet0

this is the way you can run the newly created vm in gui format
To run vm in headless form just add the flag '-display none -daemonize' to the command and you can acess the vm on port 7922 (assuming the guest os has a ssh server already running).