+ + + + +

Qemu

Qemu can be started with: +* qemu-kvm: old versions of qemu, with KVM support +* qemu: old version of qemu +* qemu-system-i386: recent version, i386 mode +* qemu-system-x86_64: recen version, AMD64 mode

Disk file

Create a disk file

Unless you use ISO files or dd-created raw files, you may want to use qemu-img.

Some examples: +* qemu-img create base.raw 2G +* qemu-img create -f qcow2 extra.qcow2 -b base.raw -F qcow2

The format can be forced with -f [fmt] (default is raw): +* recent formats: raw, qcow2 +* legacy and third-party formats: vmdk, vdi, vhd, vhdx, qcow1, qed

Snapshot mode: create a new disk with a base image: +* -b base.img: the base image will be the main disk, but changes will be written tio the new one +* -F qcow2: backing image format is qcow2

Convert a disk file

Converting an image can be done with qemu-img convert: +* qemu-img convert input_file output_file +* qemu-img convert input_file1 input_file2... output_file: for special multi-files input formats +* qemu-img convert -c [...]: add compression (on conversion, not on usage: you may want to re-apply it once in a while)

The format can be forced with: +* -f [fmt]: input format +* -O [fmt]: output format

The default format is raw), but you may choose between: +* recent formats: raw, qcow2 +* legacy and third-party formats: vmdk, vdi, vhd, vhdx, qcow1, qed

Access the disk file (raw mode) from the Host

You need to setup the loopback device to access such a file.
+It can be easier if you setup your fstab for it.

Your system must configure the loopback device with partitions support (i.e., rc.local): +* modprobe -r loop +* modprobe loop max_part=8

Operations: +* losetup file.raw /dev/loop0 +* mount /dev/loop0p1 /mnt/loop/loop1 +* work in the mounted fs +* umount /mnt/loop/loop1 +* losetup -d /dev/loop0

Use a disk file

to add: -snapshot # discard writes (beware of ctrl+a, S : write back!)

no snapshot with blockdev...

set -- "$@" -drive file="$disk2",index=1,media=disk,format=raw

HDD="-hda $NAME.img" +HDD="-blockdev driver=raw,node-name=disk,file.driver=file,file.filename=$NAME.img"

Floppy

-drive file=/path/to/floppy.img,index=0,if=floppy,format=raw

-blockdev driver=file,node-name=f0,filename=/path/to/floppy.img -device floppy,drive=f0

Cdrom

Old (still compatible) version: +* -cdrom cd.iso

-hdb fat:rw:/tmp/fat # ??

Graphics adapter

You can choose your graphics adapter via the -vga switch: +* -vga qxl : QXL virtio via spice (recent) +* -vga virtio : normal virtio +* -vga vmware : VMWare SVGA-II compatible +* -vga std : XP+ +* -vga cirrus : old card, 256 colours

Note that regarding performances, the graphics adapter is one thing, the display is another. Even an old DOS game can be unbearably slow if you use software rendering to process its graphics output.

-display sdl: more or less required if you do any graphical thing

Sound

SOUND="-soundhw all" # old versions +SOUND="-audiodev pipewire,id=qemu"

snd= pa, pipewire, alsa, sdl...

set -- "$@" -machine pcspk-audiodev="$snd" +set -- "$@" -audiodev "$snd",id="$snd" +set -- "$@" -device adlib,audiodev="$snd" -device sb16,audiodev="$snd"

Network

NET="-net none"

Miscallenaous options

-machine accel=kvm,XXX

RAM="-m 64m"

-boot order=dac -k fr-be -usb -usbdevice tablet -serial stdio -name "$NAME"

Script

#!/bin/sh
+
+NAME=`basename "$PWD"`
+
+DISK1="$NAME".hdc
+DISK2="$NAME".hdd
+CDROM="$NAME".iso
+FLOPPY="$NAME".fdd
+
+[ "$SND" = "" ] && SND=pipewire
+[ "$RAM" = "" ] && RAM=64m
+
+set --
+set -- "$@" -machine accel=kvm
+set -- "$@" -machine pcspk-audiodev="$SND"
+set -- "$@" -audiodev "$SND",id="$SND"
+set -- "$@" -device adlib,audiodev="$SND" -device sb16,audiodev="$SND"
+set -- "$@" -boot order=dac
+set -- "$@" -m $RAM
+set -- "$@" -name "$NAME"
+set -- "$@" -display sdl
+if [ -e "$FLOPPY" ]; then
+    set -- "$@" -drive file="$FLOPPY",index=0,if=floppy,format=raw
+fi
+if [ -e "$DISK1" ]; then
+    set -- "$@" -drive file="$DISK1",index=1,media=disk,format=raw
+fi
+if [ -e "$DISK2" ]; then
+    set -- "$@" -drive file="$DISK2",index=2,media=disk,format=raw
+fi
+if [ -e "$CDROM" ]; then
+    set -- "$@" -drive file="$CDROM",index=3,media=cdrom,format=raw
+fi
+
+echo qemu-system-i386 "$@"
+qemu-system-i386 "$@"
+

+ + + + + + + + + + + + + +

Qemu

Disk file

Create a disk file

Convert a disk file

Access the disk file (raw mode) from the Host

Use a disk file

Floppy

Cdrom

-hdb fat:rw:/tmp/fat # ??

Graphics adapter

Sound

Network

Miscallenaous options

Script

Docker

Game Mode

Linux display

Scaling applications

Scaling the desktop with Xorg X11

Scaling the desktop without changing the resolution

Scaling the desktop and simulate/render a new resolution

Making xrandr changes persistent

Experiments notes