.. _datasource_lxd:

LXD
***

The LXD datasource allows the user to provide custom user data,
vendor data, metadata and network-config to the instance without running
a network service (or even without having a network at all). This datasource
performs HTTP GETs against the `LXD socket device`_ which is provided to each
running LXD container and VM as ``/dev/lxd/sock`` and represents all
instance-metadata as versioned HTTP routes such as:

  - 1.0/meta-data
  - 1.0/config/user.meta-data
  - 1.0/config/user.vendor-data
  - 1.0/config/user.user-data
  - 1.0/config/user.<any-custom-key>

The LXD socket device ``/dev/lxd/sock`` is only present on containers and VMs
when the instance configuration has ``security.devlxd=true`` (default).
Disabling the ``security.devlxd`` configuration setting at initial launch will
ensure that ``cloud-init`` uses the :ref:`datasource_nocloud` datasource.
Disabling ``security.devlxd`` over the life of the container will result in
warnings from ``cloud-init``, and ``cloud-init`` will keep the
originally-detected LXD datasource.

The LXD datasource is detected as viable by ``ds-identify`` during ``systemd``
generator time when either ``/dev/lxd/sock`` exists, or
``/sys/class/dmi/id/board_name`` matches "LXD".

The LXD datasource provides ``cloud-init`` with the ability to react to
metadata, vendor data, user data and network-config changes, and to render the
updated configuration across a system reboot.

To modify which metadata, vendor data or user data are provided to the
launched container, use either LXD profiles or
``lxc launch ... -c <key>="<value>"`` at initial container launch, by setting
one of the following keys:

- ``user.meta-data``: YAML metadata which will be appended to base metadata.
- ``user.vendor-data``: YAML which overrides any metadata values.
- ``user.network-config``: YAML representing either :ref:`network_config_v1` or
  :ref:`network_config_v2` format.
- ``user.user-data``: YAML which takes precedence and overrides both metadata
  and vendor data values.
- ``user.any-key``: Custom user configuration key and value pairs, which can be
  passed to ``cloud-init``. Those keys/values will be present in instance-data
  which can be used by both `#template: jinja` #cloud-config templates and
  the :command:`cloud-init query` command.

.. note::
   LXD version 4.22 introduced a new scope of config keys prefaced by
   ``cloud-init.``, which are preferred above the related ``user.*`` keys:

   - ``cloud-init.meta-data``
   - ``cloud-init.vendor-data``
   - ``cloud-init.network-config``
   - ``cloud-init.user-data``

Configuration
=============

By default, network configuration from this datasource will be:

.. code-block:: yaml

   version: 1
   config:
       - type: physical
         name: eth0
         subnets:
             - type: dhcp
               control: auto

This datasource is intended to replace :ref:`datasource_nocloud`
datasource for LXD instances with a more direct support for LXD APIs instead
of static NoCloud seed files.

Hotplug
=======

Network hotplug functionality is supported for the LXD datasource as described
in the :ref:`events` documentation. As hotplug functionality relies on the
cloud-provided network metadata, the LXD datasource will only meaningfully
react to a hotplug event if it has the configuration necessary to respond to
the change. Practically, this means that even with hotplug enabled, **the
default behavior for adding a new virtual NIC will result in no change**.

To update the configuration to be used by hotplug, first pass the network
configuration via the ``cloud-init.network-config`` (or
``user.network-config`` on older versions).

Example
-------

Given an LXD instance named ``my-lxd`` with hotplug enabled and
an LXD bridge named ``my-bridge``, the following will allow for additional
DHCP configuration of ``eth1``:

.. code-block:: shell-session

    $ cat /tmp/cloud-network-config.yaml
    version: 2
    ethernets:
        eth0:
            dhcp4: true
        eth1:
            dhcp4: true

    $ lxc config set my-lxd cloud-init.network-config="$(cat /tmp/cloud-network-config.yaml)"
    $ lxc config device add my-lxd eth1 nic name=eth1 nictype=bridged parent=my-bridge
    Device eth1 added to my-lxd

.. _LXD socket device: https://linuxcontainers.org/lxd/docs/master/dev-lxd