• If in headless mode, to exit the VM instance press Ctrl+A and release A but still holding Ctrl, then press C. A prompt should appear (qemu) in to which the command quit ends the VM instance.

The qemuu-img can create (create) a disk image in a specific format (-f) as a file of a specific size. For example:

• $ qemu-img create -f raw <file> 4G
• $ qemu-img create -f raw <file> 4G

Convert from one disk image format to another. For example:

• qemu-img convert -f raw -O qcow2 <file>.raw <file>.qcow2

Resize a disk image. For example:

• qemu-img resize <file>.qcow2 +10G
• qemu-img resize -f raw <file> +10G

Show information about the image qemu-img info <file>. For example,

file format: raw
virtual size: 10 GiB (10737418240 bytes)
disk size: 4 KiB

• Convert from QCOW2 to raw qemu-img convert -p -O raw file.qcow2 file.raw.
• Mount as loop device.

• List all valid sound cards qemu-system-x86_64 -soundhw help.
• The paramater -soundhw <valid sound card> is deprecated.
• Use the parameter -device <for most valid sound cards>.
  • For hda however two parameters must be provided -device intel-hda -device hda-duplex.
  • For pcspk the parameter is -machine pcspk-audiodev=<NAME>.

• PCI passthrough via OVMF

Enable IOMMU in the Linux kernel:

• AMD amd_iommu=on
• Intel intel_iommu=on

Prevent devices which cannot be passed through iommu=pt.

• Networking

• Port forward from host to guest -nic user,hostfwd=tcp::<HOST PORT>-<GUEST IP>:<GUEST PORT>.

  • The nic parameter creates a basic Network Interface Controller.

• OVMF for virtual machines

• Arch Linux pacman -S edk2-ovmf

• Copy the non-volatile variable store $ cp /usr/share/edk2-ovmf/x64/OVMF_VARS.fd ~/vm/example.qemu.OVMF_VARS.fd.

• The owner of the OVMF_VARS has to be the same as the user who will execute the Qemu instance referencing the OVMF_VARS.

• Add to qemu arguments -drive if=pflash,format=raw,readonly,file=/usr/share/edk2-ovmf/x64/OVMF_CODE.fd -drive if=pflash,format=raw,file=example.qemu.OVMF_VARS.fd.

• Qemu documentation Invocation

With UEFI support.

qemu-system-x86_64 -boot order=d -name EXAMPLE_1 \
  -enable-kvm -m 2G -cpu host -device intel-hda -k sv \
  -daemonize -vnc :1 \
  -drive if=pflash,format=raw,readonly=on,file=/usr/share/edk2-ovmf/x64/OVMF_CODE.fd \
  -drive if=pflash,format=raw,file=~/vm/example1.qemu.OVMF_VARS.fd \
  -cdrom /obj/distro/release/2020.10.01-x86_64.iso \
  -drive file=~/vm/example1.qemu.raw,format=raw,index=0,media=disk

qemu-system-x86_64 -boot order=d -name EXAMPLE_2 \
  -enable-kvm -m 2G -cpu host -device intel-hda -k sv \
  -daemonize -vnc :2 \
  -drive if=pflash,format=raw,readonly=on,file=/usr/share/edk2-ovmf/x64/OVMF_CODE.fd \
  -drive if=pflash,format=raw,file=~/vm/example2.qemu.OVMF_VARS.fd \
  -cdrom /obj/distro/release/2022.10.01-x86_64.iso \
  -drive file=~/vm/example2.qemu.raw,format=raw,index=0,media=disk

The SSH connection:

ssh -vvx -p <SSH PORT>40001 \
  -i ~/.ssh/prv/[email protected] \
  <SERVER IP>[email protected] \
  -L <SSH PORT>40001:localhost:<VNC PORT>5901 \
  -L <SSH PORT>40002:localhost:<VNC PORT>5902

The VNC connection:

/usr/bin/sh -c 'vncviewer -SecurityTypes None -AcceptClipboard -SetPrimary \
  -SendClipboard -SendPrimary -FullColor -PreferredEncoding Tight \
  -QualityLevel 9 -CompressLevel 9 -DotWhenNoCursor localhost::<SSH PORT>40001'

The ~/share on the host should become available in the guest VM instance.

-drive file=fat:rw:~/share,index=1,media=disk,format=raw

The method has some limitations. For example,

• filenames must be within the ASCII 7-bit range,
• the host cannot write to the directory when the guest is accessing the directory.