tianon/qemu

$ touch /home/jsmith/hda.qcow2
$ docker run -it --rm \
	--device /dev/kvm \
	--name qemu-container \
	-v /home/jsmith/hda.qcow2:/tmp/hda.qcow2 \
	-e QEMU_HDA=/tmp/hda.qcow2 \
	-e QEMU_HDA_SIZE=100G \
	-e QEMU_CPU=4 \
	-e QEMU_RAM=4096 \
	-v /home/jsmith/downloads/debian.iso:/tmp/debian.iso:ro \
	-e QEMU_CDROM=/tmp/debian.iso \
	-e QEMU_BOOT='order=d' \
	-e QEMU_PORTS='2375 2376' \
	tianon/qemu

Note: port 22 will always be mapped (regardless of the contents of QEMU_PORTS).

For supplying additional arguments, use a command of start-qemu <args>. For example, to use -curses, one would docker run ... tianon/qemu start-qemu -curses.

For UEFI support, the ovmf package is installed, which can be utilized most easily by supplying --bios /usr/share/ovmf/OVMF.fd.

By default, this image will use QEMU's user-mode networking stack, which means if you want ping/ICMP working, you'll likely need to also include something like --sysctl net.ipv4.ping_group_range='0 2147483647' in your container runtime settings.