cloud-init/doc/rtd/topics/datasources.rst

========= Datasources ========= ---------- What is a datasource? ----------

Datasources are sources of configuration data for cloud-init that typically come from the user (aka userdata) or come from the stack that created the configuration drive (aka metadata). Typical userdata would include files, yaml, and shell scripts while typical metadata would include server name, instance id, display name and other cloud specific details. Since there are multiple ways to provide this data (each cloud solution seems to prefer its own way) internally a datasource abstract class was created to allow for a single way to access the different cloud systems methods to provide this data through the typical usage of subclasses.

The current interface that a datasource object must provide is the following:

# returns a mime multipart message that contains
# all the various fully-expanded components that
# were found from processing the raw userdata string
# - when filtering only the mime messages targeting
#   this instance id will be returned (or messages with
#   no instance id)
def get_userdata(self, apply_filter=False)

# returns the raw userdata string (or none)
def get_userdata_raw(self)

# returns a integer (or none) which can be used to identify
# this instance in a group of instances which are typically
# created from a single command, thus allowing programatic
# filtering on this launch index (or other selective actions)
@property
def launch_index(self)

# the data sources' config_obj is a cloud-config formated
# object that came to it from ways other than cloud-config
# because cloud-config content would be handled elsewhere
def get_config_obj(self)

#returns a list of public ssh keys
def get_public_ssh_keys(self)

# translates a device 'short' name into the actual physical device
# fully qualified name (or none if said physical device is not attached
# or does not exist)
def device_name_to_device(self, name)

# gets the locale string this instance should be applying 
# which typically used to adjust the instances locale settings files
def get_locale(self)

@property
def availability_zone(self)

# gets the instance id that was assigned to this instance by the 
# cloud provider or when said instance id does not exist in the backing
# metadata this will return 'iid-datasource'
def get_instance_id(self)

# gets the fully qualified domain name that this host should  be using
# when configuring network or hostname releated settings, typically
# assigned either by the cloud provider or the user creating the vm
def get_hostname(self, fqdn=False)

def get_package_mirror_info(self)

EC2

The EC2 datasource is the oldest and most widely used datasource that cloud-init supports. This datasource interacts with a magic ip that is provided to the instance by the cloud provider. Typically this ip is 169.254.169.254 of which at this ip a http server is provided to the instance so that the instance can make calls to get instance userdata and instance metadata.

Metadata is accessible via the following URL:

GET http://169.254.169.254/2009-04-04/meta-data/
ami-id
ami-launch-index
ami-manifest-path
block-device-mapping/
hostname
instance-id
instance-type
local-hostname
local-ipv4
placement/
public-hostname
public-ipv4
public-keys/
reservation-id
security-groups

Userdata is accessible via the following URL:

GET http://169.254.169.254/2009-04-04/user-data
1234,fred,reboot,true | 4512,jimbo, | 173,,,

Note that there are multiple versions of this data provided, cloud-init by default uses 2009-04-04 but newer versions can be supported with relative ease (newer versions have more data exposed, while maintaining backward compatibility with the previous versions).

To see which versions are supported from your cloud provider use the following URL:

GET http://169.254.169.254/
1.0
2007-01-19
2007-03-01
2007-08-29
2007-10-10
2007-12-15
2008-02-01
2008-09-01
2009-04-04
...
latest

Config Drive

OpenNebula

Alt cloud

No cloud

MAAS

TODO

For now see: http://maas.ubuntu.com/

CloudStack

TODO

OVF

TODO

For now see: https://bazaar.launchpad.net/~cloud-init-dev/cloud-init/trunk/files/head:/doc/sources/ovf/

Fallback/None

This is the fallback datasource when no other datasource can be selected. It is the equivalent of a empty datasource in that it provides a empty string as userdata and a empty dictionary as metadata. It is useful for testing as well as for when you do not have a need to have an actual datasource to meet your instance requirements (ie you just want to run modules that are not concerned with any external data). It is typically put at the end of the datasource search list so that if all other datasources are not matched, then this one will be so that the user is not left with an inaccessible instance.

Note: the instance id that this datasource provides is iid-datasource-none.