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.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 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 the detect stage 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:

  • cloud-init.vendor-data: YAML which overrides any metadata values.

  • cloud-init.network-config: YAML representing either Networking config Version 1 or Networking config Version 2 format.

  • cloud-init.user-data: YAML which takes precedence and overrides both metadata and vendor data values.

  • user.<any-key>: Keys prefixed with user. are included in instance data under the ds.config key. These key value pairs are used in jinja cloud-config and user data scripts. These key-value pairs may be inspected on a launched instance using cloud-init query ds.config.

Note

Periods (.) and hyphens (-) in Jinja2 have special meaning. Keys which contain a period or hyphen cannot use dot notation to access nested values. To support dot notation, cloud-init provides an alias by converting each hyphen (-) and period (.) character to an underscore (_). This means that an instance launched with -c user.special-key=1FE321 can be queried using standard jinja notation, cloud-init query --format "{{ds.config['user.special-key']}}" or may use the alias notation cloud-init query --format "{{ds.config.user_special_key}}" or cloud-init query ds.config.user_special_key.

Configuration

By default, network configuration from this datasource will be:

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

This datasource is intended to replace 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 Events and updates 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:

$ 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