## Graphical Installation ##

Bellow instructions are for creating a kvm guest OS(Debian) on Debian.
Though the examples are based on Debian it should be same for all other
distro.

* Check if your CPU support virtualization: `grep -E --color=auto 'vmx|svm|0xc0f' /proc/cpuinfo`

* Check if the host kernel support KVM: `grep CONFIG_KVM /boot/config-$(uname -r)`

* Install necessary packages for QEMU/KVM: `sudo apt install qemu-system`

* Create a qcow2 image for the guest: `qemu-img create -f qcow2 virtualdebian.img 50G`

* Boot ISO to install the guest OS: (You need to run this as root for networking to work)
```
sudo qemu-system-x86_64 -enable-kvm -m RAM_IN_MB -smp NUM_CPU -drive file=virtualdebian.img -cdrom debian.iso -boot d
```

* Install guest OS.

* Now run the guest OS with qemu whenever you want:
```
sudo qemu-system-x86_64 -enable-kvm -m 2048 -cpu host -smp 2 -drive file=virtualdebian.img
```
* If you want to share a folder from host to guest:
    1. Run the guest with this command:
    ```
    sudo qemu-system-x86_64 -enable-kvm -m 2048 -cpu host -smp 2 -drive file=virtualdebian.img,if=virtio -fsdev local,security_model=passthrough,id=fsdev0,path=/path/to/host/folder -device virtio-9p-pci,id=fs0,fsdev=fsdev0,mount_tag=hostshare
    ```
    2. In guest mount the host folder: `mount -t 9p -o trans=virtio,version=9p2000.L hostshare /path/to/mount/point`

* A better alternative for sharing file would be [virtiofs](https://virtio-fs.gitlab.io/index.html): Needs testing.

## CLI installation (-nographic) ##

Debian netinst doesn't show any output if qemu is run with -nographic option while installing from ISO. You have to use `-kernel /path/to/kernel` with `-append "console=ttyS0"`. Other Solutions:

* https://sites.google.com/a/palatin.fr/pierre/entries/debian-netinst-qemu
* https://superuser.com/a/1311906/460620
* https://levelup.gitconnected.com/probably-the-simplest-way-to-install-debian-ubuntu-in-qemu-2db6afde27ef
* https://serverfault.com/questions/976140/how-do-i-boot-the-debian-10-image-with-qemu-kvm

Once the installation is done you can start the VM normally.

## ARM ##

#### Running Ubuntu on Qemu ###

* Download Ubuntu ARM cloud image: http://cloud-images.ubuntu.com/
* Create UEFI image for qemu:

```
sudo apt-get install qemu-efi
cp /usr/share/qemu-efi-aarch64/QEMU_EFI.fd flash0.img
truncate -s 64M flash0.img
truncate -s 64M flash1.img
```
* Run Ubuntu cloud image with QEMU:

```
qemu-system-aarch64 -m 8G -cpu cortex-a57 -M virt,gic-version=max -smp 16 -nographic -drive if=pflash,format=raw,file=flash0.img,readonly -drive if=pflash,format=raw,file=flash1.img -drive if=none,file=focal-server-cloudimg-arm64.img,id=hd0 -device virtio-blk-device,drive=hd0
```

* [Installing Debian on QEMU’s 64-bit ARM “virt” board](https://web.archive.org/web/20220704230751/https://translatedcode.wordpress.com/2017/07/24/installing-debian-on-qemus-64-bit-arm-virt-board/)
* [Build an aarch64 UEFI image for QEMU](http://www.xryan.net/p/212)
* [Ubuntu ARM on Qemu](https://wiki.ubuntu.com/ARM64/QEMU)
* [How to install Ubuntu Server for Arm in a QEMU aarch64 virtual machine](https://lanyaplab.com/index.php/2020/06/08/how-to-install-ubuntu-server-for-arm-in-a-qemu-aarch64-virtual-machine/)
* [QEMU ARM limit of 123 cores ](https://futurewei-cloud.github.io/ARM-Datacenter/qemu/qemu-arm-about-the-123-core-limit/): Use GIC to scale more than 8 processors

## Miscellaneous ##

* Audio: -soundhw ac97
* Increase Resolution: `-vga virtio`
* Better Graphics Support: https://www.linux-kvm.org/page/SPICE
* [How to mount a qcow2 disk image](https://gist.github.com/shamil/62935d9b456a6f9877b5)
* [Changing the password Qemu kvm qcow2 ](https://access.redhat.com/discussions/664843): Uses tool `guestfish` but simply mounting the image and editing /etc/shadow directly with a text editor will work too.

## Compiling the kernel ##

* https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/tree/README?id=refs/tags/v4.3.3
* https://www.linux.com/topic/desktop/how-compile-linux-kernel-0/
* https://wiki.archlinux.org/title/Kernel/Traditional_compilation
* https://unix.stackexchange.com/questions/253245/what-does-make-localmodconfig-do
* https://tldp.org/HOWTO/pdf/Modules.pdf
* [How to debug kernel using QEMU and aarch64 VM](https://futurewei-cloud.github.io/ARM-Datacenter/qemu/aarch64-debug-kernel/)

**Quick Configure, build and install**
```
make olddefconfig
make localmodconfig
make -j$(nproc)
make -j$(nproc) bzImage # If you want to create kernel bzImage
make modules
make modules_install
make install
```

## Running the compiled kernel and Debugging ##

* [Direct Linux Boot](https://qemu-project.gitlab.io/qemu/system/linuxboot.html)
* [Prepare the environment for developing Linux kernel with qemu.](https://medium.com/@daeseok.youn/prepare-the-environment-for-developing-linux-kernel-with-qemu-c55e37ba8ade)
* [Booting a Custom Linux Kernel in QEMU and Debugging It With GDB](http://nickdesaulniers.github.io/blog/2018/10/24/booting-a-custom-linux-kernel-in-qemu-and-debugging-it-with-gdb/)

## Automating QEMU ###

* [qemu guest automation](https://stackoverflow.com/questions/3146013/qemu-guest-automation)
* [Is it possible to script qemu?](https://stackoverflow.com/questions/5271647/is-it-possible-to-script-qemu)
* [How to Setup QEMU Output to Console and Automate Using Shell Script](https://fadeevab.com/how-to-setup-qemu-output-to-console-and-automate-using-shell-script/#binariesusedinexamples)
* [Automating the Creation of QEMU Archlinux Images from Scratch](https://blog.stefan-koch.name/2020/05/31/automation-archlinux-qemu-installation)
* [Automating Debian install in QEMU](https://sigmaris.info/blog/2019/04/automating-debian-install-qemu/)

## General References ##
1. https://wiki.debian.org/KVM
2. https://wiki.debian.org/QEMU
3. https://wiki.archlinux.org/index.php/KVM
4. https://wiki.archlinux.org/index.php/QEMU
5. https://wiki.gentoo.org/wiki/QEMU/Options
6. https://www.tauceti.blog/posts/qemu-kvm-share-host-directory-with-vm-with-virtio/
7. [QEMU Disk Images](https://qemu-project.gitlab.io/qemu/system/images.html)