QEMU in Docker

QEMU in a docker container for running x64 virtual machines (even on ARM platforms).

It uses high-performance QEMU options (like KVM acceleration, kernel-mode networking, IO threading, etc.) to achieve near-native speed.

Features

• Multi-platform
• KVM acceleration
• Web-based viewer

Usage

Via docker-compose.yml

version: "3"
services:
  qemu:
    container_name: qemu
    image: qemux/qemu-docker
    environment:
      DISPLAY: "vnc"
      BOOT: "https://dl-cdn.alpinelinux.org/alpine/v3.19/releases/x86_64/alpine-virt-3.19.0-x86_64.iso"
    devices:
      - /dev/kvm
    cap_add:
      - NET_ADMIN
    ports:
      - 2222:22
      - 5900:5900
    stop_grace_period: 2m
    restart: unless-stopped

Via docker run

docker run -it --rm -e "DISPLAY=vnc" -e "BOOT=http://example.com/image.iso" -p 5900:5900 --device=/dev/kvm --cap-add NET_ADMIN qemux/qemu-docker

FAQ

• How do I specify the boot disk?

  You can modify the BOOT environment variable to specify the URL of an ISO image:

  environment:
    BOOT: "https://dl-cdn.alpinelinux.org/alpine/v3.19/releases/x86_64/alpine-virt-3.19.0-x86_64.iso"
  

  It will be downloaded only once, during the initial run of the container.

  Alternatively, you can place a file called boot.img in the /storage folder if you want to use a local image instead.

• How do I interact with the VM?

  If you just need text-based output, you can use the Docker console or connect via SSH.

  If you need graphical output, you can enable VNC by adding the following lines to your compose file:

  environment:
    DISPLAY: "vnc"
  ports:
    - 5900:5900
  

  If you want to enable the web-based VNC viewer so that you do not need to install any client software, add the following lines to your compose file instead:

  environment:
    DISPLAY: "web"
  ports:
    - 8006:8006
  

  Afterwards you can visit http://localhost:8006/ using any web browser to view the screen of the VM and interact with it via the keyboard or mouse.

• How do I increase the amount of CPU or RAM?

  By default, a single CPU core and 1 GB of RAM are allocated to the container.

  To increase this, add the following environment variables:

  environment:
    RAM_SIZE: "4G"
    CPU_CORES: "4"
  

• How do I change the size of the data disk?

  To expand the default size of 16 GB, add the DISK_SIZE setting to your compose file and set it to your preferred capacity:

  environment:
    DISK_SIZE: "128G"
  

  This can also be used to resize the existing disk to a larger capacity without any data loss.

• How do I change the location of the data disk?

  To change the location of the data disk, include the following bind mount in your compose file:

  volumes:
    - /var/qemu:/storage
  

  Replace the example path /var/qemu with the desired storage folder.

• How do I boot Windows?

  For emulating Windows, there is dockur/windows, which is more dedicated to that purpose. It has all the same features as this container, but additionally includes a TPM emulator, all the necessary drivers, and it will even automatically download the correct ISO file from the Microsoft servers.

• How do I verify if my system supports KVM?

  To verify if your system supports KVM, run the following commands:

  sudo apt install cpu-checker
  sudo kvm-ok
  

  If you receive an error from kvm-ok indicating that KVM acceleration can't be used, check the virtualization settings in the BIOS.

• How do I assign an individual IP address to the container?

  By default, the container uses bridge networking, which shares the IP address with the host.

  If you want to assign an individual IP address to the container, you can create a macvlan network as follows:

  docker network create -d macvlan \
      --subnet=192.168.0.0/24 \
      --gateway=192.168.0.1 \
      --ip-range=192.168.0.100/28 \
      -o parent=eth0 vlan
  

  Be sure to modify these values to match your local subnet.

  Once you have created the network, change your compose file to look as follows:

  services:
    qemu:
      container_name: qemu
      ..<snip>..
      networks:
        vlan:
          ipv4_address: 192.168.0.100
  
  networks:
    vlan:
      external: true
  

  An added benefit of this approach is that you won't have to perform any port mapping anymore, since all ports will be exposed by default.

  Please note that this IP address won't be accessible from the Docker host due to the design of macvlan, which doesn't permit communication between the two. If this is a concern, you need to create a second macvlan as a workaround.

• How can the VM acquire an IP address from my router?

  After configuring the container for macvlan (see above), it is possible for the VM to become part of your home network by requesting an IP from your router, just like your other devices.

  To enable this feature, add the following lines to your compose file:

  environment:
    DHCP: "Y"
  device_cgroup_rules:
    - 'c *:* rwm'
  

  Please note that in this mode, the container and the VM will each have their own separate IPs. The container will keep the macvlan IP, and the VM will be reachable via the DHCP IP.

• How do I boot with UEFI?

  To enable UEFI booting, add the following line to your compose file:

  environment:
    BOOT_MODE: "uefi"
  

• How do I provide custom arguments to QEMU?

  You can create the ARGUMENTS environment variable to provide additional arguments to QEMU at runtime:

  environment:
    ARGUMENTS: "-device usb-tablet"