OpenWrt in QEMU

This document descripes howto run the OpenWrt x86 port in QEMU.

  • qemu an example setup

It is mixed descriptions from windows and linux, so please read through all of it before starting.

:!: Choosing different emulation settings can affect performance greatly.

Example: 30s iperf-s@openwrt(qemu running on host) to host

ne2k_pci:0.0-31.3 sec  14.6 MBytes  3.92 Mbits/sec
pcnet: 0.0-30.0 sec  2.38 GBytes   682 Mbits/sec
e1000: 0.0-30.0 sec  6.23 GBytes  1.79 Gbits/sec
vmxnet3: 0.0-30.0 sec  8.67 GBytes  2.48 Gbits/sec
virtio-net-pci:  0.0-30.0 sec  44.6 GBytes  12.8 Gbits/sec

Getting QEMU

Ubuntu Linux version

Many Linux Distributions like Debian, Ubuntu, Suse, Fedora provide a qemu package in their package repositories.

Example for Debian 7 (Wheezy):

sudo apt-get install qemu

:!: Qemu is rapidly developing so features, syntax might change between versions.

Windows version

QEMU is an an open source processor emulator (and virtualizer). The QEMU Wiki Links page provides you with several unoffical download links of Windows builds.

Kamikaze X86 example

In this example download the and unzip to a directory.

Download OpenWrt raw image (ex. kamikaze/8.09.1/x86/) and copy the raw image into the qemu directory.

Run QEMU by using following command:

C:\qemu-0.9.0-windows>qemu.exe -L . -hda openwrt-x86-ext2.image

Which shall result in a command window as shown below:

Start QEMU with OpenWrt

QEMU may issue warning message as following:

Could not open '\\.\kqemu' - QEMU acceleration layer not activated

You may correct this warning by installing KQEMU driver which provides better performance for the VM, but this is not as relevant to OpenWrt.

Upon execution of the above command new window shall appear with booting OpenWrt:

OpenWrt boot up

And in several seconds OpenWrt VM shall be up and running:

OpenWrt running in QEMU

OpenWrt in QEMU ARM

The "realview" platform is meant for use with QEMU for emulating an ARM system. This platform might not be available in the standard downloads (it isn't at time of writing), but it currently appears when building from scratch.

As of QEMU 1.1.2, use the following on the command line to get it booting:

qemu-system-arm -M realview-eb-mpcore -kernel openwrt-realview-vmlinux.elf -net nic -net user -nographic

Basically, use the generated image as the `-kernel` parameter.

FIXME Trunk: kernel image does not boot; initramfs image works FIXME Trunk: untested: use SD card with rootfs, NFS rootfs, NBD rootfs FIXME Trunk: no sound, pcibus, usb emulation in qemu possible?

OpenWrt in QEMU MIPS

The "malta" platform is meant for use with QEMU for emulating a MIPS system.

:!: The malta platform is broken in trunk since gcc was switched to 4.8. Compile with gcc 4.6 to get it working or disable MIPS16. ticket #16881

depending on the malta variant

qemu-system-mipsel -kernel openwrt-malta-le-vmlinux-initramfs.elf -nographic -m 256

OpenWrt in QEMU X86-64

The x86-64 target has support for ESXI images by default. Booting the VMDK / VDI images might not work with newer qemu versions.

qemu-system-x86_64 2.0.0 with defaullt machine does not seem to work with simple "-hda openwrt.vdi".

pc-q35-2.0 emulates a different machine. With new syntax (no -hda , -net) the VDI / VMDK works.


  • 2 HDDs (1 openwrt image, 1 data)
  • 1 drive per bus, 6 bus available (until ide.5)
  • 2 Network cards : 1 bridged to host (need higher permission) and 1 "user" (default, NAT 10.x.x.x)

Some emulated network cards might have performance issues.

qemu-system-x86_64 \
-enable-kvm \
-M pc-q35-2.0 \
-drive file=openwrt-x86_64-combined-ext4.vdi,id=d0,if=none \
-device ide-hd,drive=d0,bus=ide.0 \
-drive file=data.qcow2,id=d1,if=none \
-device ide-hd,drive=d1,bus=ide.1 \
-soundhw ac97 \
-netdev bridge,br=virbr0,id=hn0 \
-device e1000,netdev=hn0,id=nic1 \
-netdev user,id=hn1 \
-device e1000,netdev=hn1,id=nic2

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doc/howto/qemu.txt · Last modified: 2014/07/10 22:04 by theoradicus