CheatPress

QEMU Machine emulator and virtualizer

Version 11.1 · source

QEMU, Postcard, light preview Light · Postcard 102 × 152 mm · PDF QEMU, Postcard, dark preview Dark · Postcard 102 × 152 mm · PDF QEMU, Postcard, ink saver preview Ink saver · Postcard 102 × 152 mm · PDF
QEMU, A5, light preview Light · A5 148 × 210 mm · PDF QEMU, A5, dark preview Dark · A5 148 × 210 mm · PDF QEMU, A5, ink saver preview Ink saver · A5 148 × 210 mm · PDF
QEMU, A4, light preview Light · A4 210 × 297 mm · PDF QEMU, A4, dark preview Dark · A4 210 × 297 mm · PDF QEMU, A4, ink saver preview Ink saver · A4 210 × 297 mm · PDF
QEMU, A4 landscape, light preview Light · A4 landscape 297 × 210 mm · PDF QEMU, A4 landscape, dark preview Dark · A4 landscape 297 × 210 mm · PDF QEMU, A4 landscape, ink saver preview Ink saver · A4 landscape 297 × 210 mm · PDF
QEMU, A3, light preview Light · A3 297 × 420 mm · PDF QEMU, A3, dark preview Dark · A3 297 × 420 mm · PDF QEMU, A3, ink saver preview Ink saver · A3 297 × 420 mm · PDF
QEMU, A3 landscape, light preview Light · A3 landscape 420 × 297 mm · PDF QEMU, A3 landscape, dark preview Dark · A3 landscape 420 × 297 mm · PDF QEMU, A3 landscape, ink saver preview Ink saver · A3 landscape 420 × 297 mm · PDF
QEMU, Letter, light preview Light · Letter 8.5 × 11 in · PDF QEMU, Letter, dark preview Dark · Letter 8.5 × 11 in · PDF QEMU, Letter, ink saver preview Ink saver · Letter 8.5 × 11 in · PDF
QEMU, Tabloid, light preview Light · Tabloid 11 × 17 in · PDF QEMU, Tabloid, dark preview Dark · Tabloid 11 × 17 in · PDF QEMU, Tabloid, ink saver preview Ink saver · Tabloid 11 × 17 in · PDF

Start here

qemu-img create -f qcow2 <disk.qcow2> 20G
Make a virtual disk
qemu-system-x86_64 -cdrom <install.iso> -hda <disk.qcow2> -m 2G -boot d
Install an OS
qemu-system-x86_64 -accel kvm -cpu host -m 4G -smp 4 -hda <disk.qcow2>
Run it fast
-nic user,hostfwd=::2222-:22
SSH into the guest
-nographic
Run in the terminal
Ctrl+a x
Quit a -nographic guest
qemu-img info <disk>
Size, format, backing
-snapshot
Throw away changes

Concepts

Host Linux, /dev/kvm
qemu-system-* one process per VM
Machine -machine, -cpu, -m, -smp
Devices -drive, -netdev, -device

Run a VM

qemu-system-x86_64 -hda <disk>
Boot from a disk image
-accel kvm
Hardware acceleration (Linux)
Needs access to /dev/kvm. -enable-kvm is the older spelling of the same thing.
-cpu host
Pass the host CPU model through
-m <size>
Guest RAM, e.g. 2G
-smp <n>
Number of virtual CPUs
-name <vm>
Name the VM (window, process)
-machine q35
Pick a modern chipset
-machine help
List machine types
-daemonize
Detach into the background
-loadvm <tag>
Start from a saved snapshot

Disks and boot

-drive file=<disk>,format=qcow2,if=virtio
Attach a virtio disk
-cdrom <iso>
Attach an optical image
-boot d
Boot from the CD first
-boot order=<cdn>
Set boot device order
-snapshot
Discard disk writes on exit
Writes go to temporary files; press Ctrl+a s in the console or run commit in the monitor to keep them.
-drive file=<disk>,cache=none,aio=native
Direct I/O for speed
-drive if=pflash,format=raw,readonly=on,file=<OVMF_CODE.fd>
UEFI firmware (OVMF)
-kernel <bzImage> -append "<cmdline>"
Boot a kernel directly

Display and console

-nographic
No window; serial on the terminal
-display gtk
Choose the display backend
-display vnc=:<n>
VNC server on port 5900+n
-vga virtio
Pick the virtual graphics card
-serial mon:stdio
Serial and monitor on the terminal
-monitor stdio
Monitor on the terminal
-qmp unix:<sock>,server,nowait
Machine-readable control socket

Network

-nic user
Simple NAT, no setup (default)
-nic user,hostfwd=::<host>-:<guest>
Forward a host port to the guest
-nic user,model=virtio-net-pci
Choose the NIC model
-nic tap,script=no,ifname=<tap>
Attach to a host tap device
-nic bridge,br=<br0>
Join a host bridge (needs helper)
-netdev user,id=<n0>,hostfwd=tcp::<host>-:<guest>
Same, long form
-device virtio-net-pci,netdev=<n0>
Pair a NIC with a -netdev

Devices and sharing

-device help
List available devices
-usb
Enable the USB controller
-device usb-host,vendorid=<vid>,productid=<pid>
Pass a host USB device through
-virtfs local,path=<dir>,mount_tag=<tag>,security_model=mapped-xattr
Share a folder with the guest (9p)
-device vfio-pci,host=<bdf>
PCI passthrough

qemu-img

qemu-img create -f qcow2 <disk> <size>
New disk image
qemu-img info <disk>
Show format and sizes
qemu-img convert -O qcow2 <in> <out>
Convert between formats
qemu-img convert -c -p -O qcow2 <in> <out>
Compress with progress
qemu-img resize <disk> +<size>
Grow an image
Shrinking needs --shrink and will destroy data past the new end unless the guest filesystem was shrunk first.
qemu-img create -f qcow2 -b <base> -F qcow2 <overlay>
Overlay on a backing file
qemu-img info --backing-chain <disk>
Show the whole overlay chain
qemu-img commit <overlay>
Merge overlay into its base
qemu-img check <disk>
Check for corruption
qemu-img snapshot -l <disk>
List internal snapshots
qemu-img snapshot -c <tag> <disk>
Create a snapshot
qemu-img snapshot -a <tag> <disk>
Restore a snapshot
qemu-img convert -f raw -O qcow2 <in.img> <out.qcow2>
Raw to qcow2
Common image formats
-f / -O Use for
raw Plain bytes, fastest, no features
qcow2 Sparse, snapshots, backing files
vmdk VMware images
vdi VirtualBox images
vhdx Hyper-V images

Monitor

Ctrl+a c
Switch console / monitor (mon:stdio)
Ctrl+a x
Exit the emulator
info status
Running or paused?
info block
Show attached drives
info network
Show network devices
stop / cont
Pause / resume the guest
savevm <tag>
Save full VM state (needs qcow2)
loadvm <tag>
Restore VM state
delvm <tag>
Delete a saved state
system_powerdown
Send an ACPI power button press
system_reset
Hard reset
quit
Kill the VM now
change <dev> <file>
Swap the medium in a drive
device_add <driver>,id=<id>
Hotplug a device

Recipes

Install an OS
qemu-img create -f qcow2 vm.qcow2 20Gqemu-system-x86_64 \  -accel kvm -cpu host -m 4G \  -drive file=vm.qcow2,if=virtio \  -cdrom <install.iso> -boot d
Headless VM with SSH
qemu-system-x86_64 -nographic \  -accel kvm -cpu host -m 2G \  -drive file=vm.qcow2,if=virtio \  -nic user,hostfwd=::2222-:22# then, from the hostssh -p 2222 <user>@localhost
Disposable test run
qemu-img create -f qcow2 \  -b base.qcow2 -F qcow2 t.qcow2qemu-system-x86_64 -accel kvm \  -m 2G -drive file=t.qcow2,if=virtiorm t.qcow2
Boot a kernel in the terminal
qemu-system-x86_64 -nographic \  -accel kvm -m 1G \  -kernel <bzImage> \  -append "console=ttyS0 root=/dev/vda" \  -drive file=<rootfs>,format=raw,if=virtio