Deploying LXC devices

LXC is a userspace interface for the Linux kernel containment features. Through a powerful API and simple tools, it lets Linux users easily create and manage system or application containers. LXC devices can run lava tests within a container without disturbing the dispatcher host. The prime advantage of having LXC device in LAVA is the ability to provide a transparent, sandboxed environment with support for different OS types, enabling testing in different platforms.


Ensure that LXC is installed in your LAVA dispatcher host, if not use the following command to install LXC in Debian:

$ sudo apt install lxc

Refer the following links in order to setup networking for LXC in Debian:

Android testing with LXC support

LXC protocol is used for Android testing use-cases which removes the need for writing complex job definitions using Multinode. This is made possible by adding the usb path of the DUT that is attached to the dispatcher. The device configuration takes a special parameter called device_info which will be used to expose the DUT to LXC for Android testing. The device_info takes a list of dictionaries, where each dictionary value can contain keys such as board_id, usb_vendor_id, usb_product_id.

Examples of device_info configuration are as follows.

Example 1 - Single device with just board_id

{% set device_info = [{'board_id': '0123456789'}] %}

Example 2 - Single device with board_id and usb_vendor_id

{% set device_info = [{'board_id': '0123456789', 'usb_vendor_id': '0451'}] %}

Example 3 - Single device with board_id, usb_vendor_id and usb_product_id

{% set device_info = [{'board_id': '0123456789', 'usb_vendor_id': '0451', 'usb_vendor_id': 'd109'}] %}


Do not run adb daemon on the dispatcher host, which will grab the DUT and will hinder exposing it to LXC. Similarly, remove fastboot packages from the dispatcher host.

    connect: telnet localhost 0000
    hard_reset: /usr/bin/pduclient --daemon services --hostname pdu00 --command reboot --port 00
    power_off: /usr/bin/pduclient --daemon services --hostname pdu00 --command off --port 00
    power_on: /usr/bin/pduclient --daemon services --hostname pdu00 --command on --port 00
    pre_power_command: /usr/local/lab-scripts/usb_hub_control -p 0000 -m sync -u 00
device_type: hi6220-hikey
adb_serial_number: 12312BA123B123B1
fastboot_serial_number: 12312BA123B123B1
fastboot_options: ['-S', '256M']
device_info: [{'board_id': '12312BA123B123B1'}]  # It is a list of dictionaries

          interrupt_prompt: "Android Fastboot mode"
          interrupt_string: 'x'
            - "["
            - "]"
          item_class: '0-9'
          separator: ' '
          label_class: 'a-zA-Z0-9\s\:'
          bootloader_prompt: 'Start:'
          boot_message: "Booting Linux Kernel..."
          send_char: True
          character_delay: 10
        - select:
             - 'boot from eMMC'

      seconds: 120
      seconds: 45
      seconds: 600
      seconds: 10

Arbitrary USB devices with LXC support

Some workers have other USB devices attached, for example an energy probe, which also need to be added to the LXC for access by the test shell. These can be added as supplementary device_info dictionaries. In the case of an energy probe, the probe may be measuring a single DUT whilst being connected to the worker as a USB device. The id of that USB device needs to be in the device_info of the DUT so that the test shell running in the LXC can control the probe.

The keys given in the dictionary are not arbitrary and follow the same rules as for Android devices:

[{'board_id': '0123456789ABCDEF'}, {'board_id': 'S/NO44440001'}]


Ensure that the device_info relates to a USB device which is attached to the same worker as the DUT but is not a DUT itself.

The value to specify is what shows up in pyudev bindings as the ID_SERIAL_SHORT. This is typically the SerialNumber reported by dmesg but it is worth checking:

>>> import pyudev
>>> context = pyudev.Context()
>>> [ device.get('ID_SERIAL_SHORT') for device in context.list_devices(subsystem='usb')]
[u'0000:00:1a.0', None, None, None, None, u'889FFAE94013', None, None, None, None,
None, u'FTGNRL22', None, None, None, None, None, None, None, None, None, None, None,
None, None, None, None, None, u'0000:00:1d.0', None, None, None]

For usb_vendor_id, the corresponding pyudev key is ID_VENDOR_ID. For usb_product_id, the corresponding pyudev key is ID_MODEL_ID.

If using multiple keys for the same device_info, ensure that the key value pairs are in a single dictionary within the list of dictionaries:

{% set device_info = [{'board_id': '0123456789'}, {'board_id': 'adsd0978775', 'usb_vendor_id': 'ACME54321'}] %}


Devices which include a forward slash / in the serial number will have that replaced by an underscore when processed through pyudev. e.g.:

udev: ATTRS{serial}=="S/NO44440001"
pydev: S_NO44440001
device_info: {% set device_info = [{'board_id': 'S_NO44440001'}] %}

Configuration: Persistent Containers

A test job can request a persistent container which will not get destroyed after the test job is complete. This allows the container to be reused for subsequent test jobs. This is useful when users want to setup some software on a container and use it for subsequent test jobs without re-creating the setup every time, which may prove time consuming.

In such a case the admins can choose to switch the container creation path from the default i.e., /var/lib/lxc to some other path, which could be a larger partition mounted on the dispatcher to give more space for such persistent container users. To set a different container creation path on a per dispatcher basis lxc_path key is used in the dispatcher configuration as described in Extra dispatcher configuration

Once the lxc_path key is set in dispatch configuration, both persistent and non-persistent containers will get created in this path.


LAVA does not have a mechanism to limit the amount of disk space such persistent containers could use. Hence, administrators should setup some kind of external monitoring in order to watch the size of these persistent containers and free space whenever required or destroy unused persistent containers.

Configuration: Unprivileged containers as root

This is the recommended configuration for running your LXC devices within a LAVA dispatcher, provided your container does not access any devices attached to the host. In this configuration the containers will run as unprivileged user started by root user.

Allocate additional uids and gids to root:

$ sudo usermod --add-subuids 100000-165536 root
$ sudo usermod --add-subgids 100000-165536 root

Then edit /etc/lxc/default.conf and append lxc.uidmap entry like below:

lxc.id_map = u 0 100000 65536
lxc.id_map = g 0 100000 65536

With the above in place any container created as root will be an unprivileged container.


Do not use unprivileged containers when your container has to interact with a DUT that is attached to the host machine.


To apply configurations system wide for all LXC devices attached to the dispatcher use /etc/lxc/default.conf file.