Fuchsia emulator (FEMU)

The Fuchsia emulator (FEMU) allows you to test Fuchsia components and applications without needing a Fuchsia device. FEMU is included in Fuchsia source, and it’s downloaded by jiri as part of jiri update or jiri run-hooks. It’s fetched into the Fuchsia directory /prebuilt/third_party/aemu.

You can call FEMU with fx using the fx emu command, or from the Fuchsia IDK using femu.sh.

FEMU and other emulators

FEMU is the default emulator for Fuchsia. FEMU is based on the Android Emulator (AEMU), which is a fork of QEMU. Due to legacy issues, there may be references to AEMU in the code and documentation.

In some instances, such as emulating Zircon, you must use QEMU instead.

FEMU Features

FEMU looks and behaves like a Fuchsia device, with the exception that no paving is required.

FEMU features include:

  • GUI Support: You can run Fuchsia with the GUI (by default) or without the GUI (using the --headless argument with the fx emu command)
  • GPU Support: You can run with the host’s GPU (by default) with full Vulkan support, or you can choose software rendering using SwiftShader.
  • Remote Development: You can use a remote desktop with FEMU, either with Chrome Remote Desktop or from the command line using fx emu-remote command or femu.sh with the Fuchsia IDK.

To configure these features, see the Running Fuchsia Emulator page. Additional features are listed in the fx emu reference page. If you’re using the Fuchsia IDK, femu.sh supports the same flags as fx emu.

FEMU limitations

FEMU image and board support

When setting up FEMU using fx emu, FEMU only supports the following boards:

  • qemu-x64
  • qemu-arm64

When using the Fuchsia IDK to set up FEMU, you are limited to the following pre-built images:

  • qemu-x64
  • workstation.qemu-x64-release
  • qemu-arm64

FEMU networking

The Fuchsia Emulator should generally be run with the -N flag that provides networking through an emulated NIC. Instructions for setting up networking for FEMU is in Setting up the Fuchsia Emulator.

Without networking, you only have an isolated serial console. With networking, your device is visible to other tools such as ssh and fx serve.

Emulating Zircon

If you only want to emulate Zircon, you must use fx qemu instead. Read Debugging the Kernel using QEMU to learn more. This is for kernel developers. Most Fuchsia developers do not need to use this workflow.

FEMU common usage

To use FEMU, you must first download the Fuchsia source and build Fuchsia.

Alternatively, you can use the Fuchsia IDK and use pre-built system images.

Then you can use FEMU to do the following: