Config Drive

The configuration drive datasource supports the OpenStack configuration drive disk.

See the config drive extension and metadata introduction in the public documentation for more information.

By default, cloud-init does always consider this source to be a full-fledged datasource. Instead, the typical behavior is to assume it is really only present to provide networking information. Cloud-init will copy off the network information, apply it to the system, and then continue on. The “full” datasource could then be found in the EC2 metadata service. If this is not the case then the files contained on the located drive must provide equivalents to what the EC2 metadata service would provide (which is typical of the version 2 support listed below)

Version 1 (Deprecated)

Note: Version 1 is legacy and should be considered deprecated. Version 2 has been supported in OpenStack since 2012.2 (Folsom).

The following criteria are required to as a config drive:

  1. Must be formatted with vfat filesystem

  2. Must contain one of the following files

/etc/network/interfaces
/root/.ssh/authorized_keys
/meta.js

/etc/network/interfaces

This file is laid down by nova in order to pass static networking information to the guest. Cloud-init will copy it off of the config-drive and into /etc/network/interfaces (or convert it to RH format) as soon as it can, and then attempt to bring up all network interfaces.

/root/.ssh/authorized_keys

This file is laid down by nova, and contains the ssk keys that were provided to nova on instance creation (nova-boot –key ….)

/meta.js

meta.js is populated on the config-drive in response to the user passing “meta flags” (nova boot –meta key=value …). It is expected to be json formatted.

Version 2

The following criteria are required to as a config drive:

  1. Must be formatted with vfat or iso9660 filesystem or have a filesystem label of config-2 or CONFIG-2

  2. The files that will typically be present in the config drive are:

openstack/
  - 2012-08-10/ or latest/
    - meta_data.json
    - user_data (not mandatory)
  - content/
    - 0000 (referenced content files)
    - 0001
    - ....
ec2
  - latest/
    - meta-data.json (not mandatory)

Keys and values

Cloud-init’s behavior can be modified by keys found in the meta.js (version 1 only) file in the following ways.

dsmode:
  values: local, net, pass
  default: pass

This is what indicates if configdrive is a final data source or not. By default it is ‘pass’, meaning this datasource should not be read. Set it to ‘local’ or ‘net’ to stop cloud-init from continuing on to search for other data sources after network config.

The difference between ‘local’ and ‘net’ is that local will not require networking to be up before user-data actions (or boothooks) are run.

instance-id:
  default: iid-dsconfigdrive

This is utilized as the metadata’s instance-id. It should generally be unique, as it is what is used to determine “is this a new instance”.

public-keys:
  default: None

If present, these keys will be used as the public keys for the instance. This value overrides the content in authorized_keys.

Note: it is likely preferable to provide keys via user-data

user-data:
  default: None

This provides cloud-init user-data. See examples for what all can be present here.