Abstract

This documentation describes how to use the primitive commands for generating Android images and running Android on virtual platform. In the end, we can see how to directly run Android Automotive OS on Xen virtual machine with QEMU command.

What’s Cuttlefish flow?

Cuttlefish allows user to use command line interface (CLI) to launch Android images on Cuttlefish virtual platform, it provides the command launch_cvd for this purpose.

The prerequisites for using the launch_cvd is Cuttlefish package. The package contains binaries and utilites. We can download the Cuttlefish package for Arm64 via http://ci.android.com/, then search the branch aosp-main-throttled and select the device target aosp_cf_arm64_only_phone-trunk_staging-userdebug .

After downloading and uncompress the Cuttlefish package, combining with Android images, we can execute the launch_cvd command to boot up Android on Cuttlefish:

$ HOME=$PWD ./bin/launch_cvd

The launch_cvd command rus two commands assemble_cvd and run_cvd in its child processes. If both commands work as expected, the Android can launch successfully on Cuttlefish machine. The assemble_cvd command generates root file system images with qcow2 overlay format, then the run_cvd command invokes the virtual machine manager (either Crosvm or QEMU) to boot the generated images on virtual machine. The diagram below shows the Cuttlefish flow.

Using assemble_cvd

Let’s we assume we work on TRS and want to run Android Automotive OS on Xen virtual machine, in this case, it’s likely we cannot directly use launch_cvd command for launching Xen virtual machine. Then we need to use assumble_cvd command to help us to generate file system images, and we can execute QEMU command to launch Xen virtual machine. This is why we need to understand how to use assumble_cvd command.

If directly run assumble_cvd command, you will receive an error log and the program exits abnormaly:

leoy@leoy-yangtze:~/Dev2/aosp_cuttlefish_test/cf$ HOME=$PWD ./bin/assemble_cvd 
12-22 15:53:35.219 665720 665720 E assemble_cvd: assemble_cvd.cc:571 assemble_cvd failed: 
12-22 15:53:35.219 665720 665720 E assemble_cvd: assemble_cvd.cc:571  | device/google/cuttlefish/host/commands/assemble_cvd/assemble_cvd.cc:484
12-22 15:53:35.219 665720 665720 E assemble_cvd: assemble_cvd.cc:571  | Result<int> cuttlefish::AssembleCvdMain(int, char **)
12-22 15:53:35.219 665720 665720 E assemble_cvd: assemble_cvd.cc:571  v CF_EXPECT(tty == 0)
12-22 15:53:35.219 665720 665720 E assemble_cvd: assemble_cvd.cc:571 stdin was a tty, expected to be passed the output of a previous stage. Did you mean to run launch_cvd?
Aborted

The log reminds user to invoke launch_cvd instead of the assemble_cvd command. But this doesn’t mean we really cannot run assemble_cvd command directly. Alternatively, we can save what’s the command and arguments into a shell script (we named it as test.sh):

HOME=$PWD ./bin/assemble_cvd --group_id=cvd_1 --report_anonymous_usage_stats=y --vm_manager=qemu_cli --webrtc_device_id=cvd_1-1 --gpu_mode=drm_virgl

Then we can use the to launch the shell script with below command. This command can help use to close stdin and direct the stdout to the pipe :

true | sh test.sh 2>&1 | cat

Using run_cvd

Same as the assemble_cvd command, it prevents to directly run the run_cvd command. If we want to directly execute it, we can use the command:

$ true | HOME=$PWD ./bin/run_cvd 2>&1 | cat

run_cvd manages backend programs internally for emulating virtual devices (e.g. for WiFi, secure devices, etc), after the configurations for the emulation, it launches VMM (QEMU or Crosvm) to kick off virtual machine instance.