Enable S5

About System S5 Support

S5 refers to the ACPI “soft off” system state. ACRN system S5 support enables you to gracefully shut down or reset the whole system when multiple VMs are running. This is done by requesting and waiting for all pre-launched and post-launched VMs to gracefully shut themselves down before the Service VM triggers a system-wide shutdown or reset.

We recommend using ACRN system S5 support to shut down or reset a system unless you have other mechanisms in place to protect external storage from being corrupted by a mechanical off.

Dependencies and Constraints

Consider the following dependencies and constraints:

  • ACRN system S5 support is hardware neutral but requires the deployment of a daemon (named Lifecycle Manager) in all VMs. The Lifecycle Manager manages power state transitions.

  • The COM2 port is reserved for the Lifecycle Manager to communicate requests and responses. Console vUARTs and inter-VM UART connections should avoid using COM2 as an interface.

  • The S5 feature needs a communication vUART to control a User VM. However, you don’t need to configure a vUART connection for S5 via the ACRN Configurator, because ACRN code already has a vUART connection between the Service VM and User VMs by default.

Example Configuration

The following steps show how to enable S5 by extending the information provided in the Getting Started Guide. The scenario has a Service VM and one Ubuntu post-launched User VM.

  1. On the development computer, build the Lifecycle Manager daemon:

    cd acrn-hypervisor
    make life_mngr

    The build generates files in the build/misc/services/life_mngr directory.

  2. Copy life_mngr.conf, s5_trigger_linux.py, life_mngr, and life_mngr.service into the Service VM and User VM.

    These commands assume you have a network connection between the development computer and target system. You can also use a USB stick to transfer files.

    scp build/misc/services/s5_trigger_linux.py acrn@<target board address>:~/
    scp build/misc/services/life_mngr acrn@<target board address>:~/
    scp build/misc/services/life_mngr.service acrn@<target board address>:~/
    scp build/misc/services/life_mngr.conf acrn@<target board address>:~/

    Log in to the target system and run the following commands:

    sudo mkdir /etc/life_mngr
    sudo mv ~/life_mngr.conf /etc/life_mngr/
    sudo mv ~/life_mngr.service /lib/systemd/system/
    sudo mv ~/life_mngr /usr/bin/
  3. Copy user_vm_shutdown.py from the development computer into the Service VM:

    scp misc/services/life_mngr/user_vm_shutdown.py acrn@<target board address>:~/
  4. ACRN code sets the COM2 (/dev/ttyS1) as the default communication port of the User VM, so we need only check the S5 vUART of the Service VM. Use the following steps to get the Service VM S5 connection information.

    Log in to the Service VM and run the command cat /etc/serial.conf to get the connection information between the Service VM and User VM. Output example:

    # User_VM_id: 1
    /dev/ttyS8 port 0X9008 irq 0 uart 16550A baud_base 115200

    This example means the Service VM uses the /dev/ttyS8 connection to the User VM’s /dev/ttyS1.

  5. Configure the S5 feature:

    1. In the Service VM, edit the following options in /etc/life_mngr/life_mngr.conf. Make sure VM_NAME is the Service VM name specified in the ACRN Configurator. Replace /dev/ttyS8 with your Service VM’s S5 vUART, if it was different from the example in the previous step.

      VM_NAME= ACRN_Service_VM
    2. In the User VM, edit the following options in /etc/life_mngr/life_mngr.conf. Replace <User VM name> with the VM name specified in the ACRN Configurator.

      VM_NAME=<User VM name>
  6. Enable life_mngr.service and restart the Service VM and User VM:

    sudo chmod +x /usr/bin/life_mngr
    sudo systemctl enable life_mngr.service
    sudo reboot
  7. To trigger a system S5, run s5_trigger_linux.py in the Service VM. The Service VM shuts down (transitioning to the S5 state) and sends a poweroff request to shut down the User VM.


The S5 state is not automatically triggered by a Service VM shutdown; you need to run s5_trigger_linux.py in the Service VM.