Fuchsia

Fuchsia emulator

The Fuchsia emulator (FEMU) is the default emulator for Fuchsia. FEMU allows you to test Fuchsia components and applications without a physical Fuchsia device.

FEMU is included in the Fuchsia source tree. FEMU is downloaded (or updated) by jiri, as part of jiri update or jiri run-hooks, and is fetched into the /prebuilt/third_party/aemu directory of your Fuchsia source tree.

You can launch FEMU using ffx emu.

FEMU, AEMU, and QEMU

FEMU is based on the Android Emulator (AEMU){:.external}, which is a fork of QEMU{:.external} – in some instances, such as debugging the Zircon kernel, you should use QEMU instead.

Due to legacy issues, there may be references to AEMU in the code and documentation.

Debugging Zircon Kernel

If you want to debug the Zircon kernel, you should 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.

Features

FEMU looks and behaves like a Fuchsia device, except that no paving or flashing is required with FEMU.

The features of FEMU include:

  • GUI Support: You can run Fuchsia with the GUI (by default) or without the GUI (using the --headless argument).
  • GPU Support: You can run with the host's GPU (by default) with full Vulkan{:.exyernal} support, or you can choose software rendering using SwiftShader{:.external}.
  • 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.

To see full list of supported flags:

ffx emu start --help

Image and board support

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

  • qemu-x64
  • qemu-arm64

With the Fuchsia SDK, FEMU supports pre-built images, including:

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

ARM64 support (qemu-arm64) is very limited and not recommended.

Use ffx product-bundle list to see the full set of available products available from the SDK, and ffx product-bundle get {{ ‘’ }}product-bundle to download those products.

Networking

The --net flag specifies the networking mode for the emulator. --net requires a value to indicate which kind of networking to implement.

--net has the following possible values:

  • tap: Attaches a Tun/Tap interface.
  • user: Sets up mapped ports through SLiRP.
  • none: Disables networking.
  • auto: Checks the host system's capabilities and selects tap if it is available or user if a Tap interface is unavailable. auto is the default.

On Linux, FEMU should generally be run with the --net tap flag that provides networking through an emulated NIC.

Note: Instructions for setting up networking for FEMU is in the Start the Fuchsia Emulator guide.

--net tap and --net user allow the emulator to be discoverable when running ffx target list. --net none disables networking, which causes the emulator to not be discoverable after running ffx target list.

If starting the emulator with ffx emu start --net user, an available TCP port from the host is picked and forwarded to the emulator's SSH port.

You can manually set the SSH address and use fx tools to interact with your emulator by running the following command:

ffx emu start --net user --port-map {{ '<var>' }}PORT-NAME{{ '</var>' }}:{{ '<var>' }}PORT-NUMBER{{ '</var>' }}

Replace the following:

  • PORT-NAME: The chosen name for the port. An example port name could be ssh.
  • PORT-NUMBER: The number of the port. An example port number is 8022.

Any named ports can be set the same way. The ports that can be mapped are named in the virtual device specification.

To verify that your fx tool is using the correct port, run the following command:

ffx target get-ssh-address

You should see the SSH address printed next to Device name.

To SSH into the emulator, run the following command:

fx shell

Unsupported CPUs

FEMU currently does not run on:

  • ARM64 processors, including the Apple M1 processor.
  • AMD processors.

Supported hardware for graphics acceleration

FEMU currently supports a limited set of GPUs on macOS and Linux for hardware graphics acceleration. FEMU uses a software renderer fallback for unsupported GPUs.

Common usage

To launch FEMU, complete the Get started with Fuchsia guide.

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

Once you're able to launch FEMU, you can perform the following tasks: