This datasource finds metadata and user data from the Azure cloud platform.
The Azure cloud platform provides initial data to an instance via an attached
CD formatted in UDF. This CD contains a
ovf-env.xml file that
provides some information. Additional information is obtained via interaction
with the “endpoint”.
Azure provides the instance metadata service (IMDS), which is a REST service
169.254.169.254 providing additional configuration information to the
Cloud-init uses the IMDS for:
Network configuration for the instance which is applied per boot.
A pre-provisioning gate which blocks instance configuration until Azure fabric is ready to provision.
Retrieving SSH public keys.
Cloud-initwill first try to utilise SSH keys returned from IMDS, and if they are not provided from IMDS then it will fall back to using the OVF file provided from the CD-ROM. There is a large performance benefit to using IMDS for SSH key retrieval, but in order to support environments where IMDS is not available then we must continue to all for keys from OVF[?]
The following configuration can be set for the datasource in system
The settings that may be configured are:
Boolean set to True to use network configuration described by Azure’s IMDS endpoint instead of fallback network config of DHCP on eth0. Default is True.
Path used to read metadata files and write crawled data.
A dictionary defining which device paths should be interpreted as ephemeral images. See cc_disk_setup module for more info.
Configuration for the datasource can also be read from a
dscfg entry in
LinuxProvisioningConfigurationSet. Content in
dscfg node is
expected to be base64 encoded YAML content, and it will be merged into the
'datasource: Azure' entry.
An example configuration with the default values is provided below:
datasource: Azure: apply_network_config: true data_dir: /var/lib/waagent disk_aliases: ephemeral0: /dev/disk/cloud/azure_resource
User data is provided to
cloud-init inside the
Cloud-init expects that user data will be provided as a base64 encoded
value inside the text child of an element named
CustomData, which is a direct child of the
LinuxProvisioningConfigurationSet (a sibling to
CustomData are provided, the behaviour is
undefined on which will be selected. In the example below, user data provided
'this is my userdata'.
<wa:ProvisioningSection> <wa:Version>1.0</wa:Version> <LinuxProvisioningConfigurationSet xmlns="http://schemas.microsoft.com/windowsazure" xmlns:i="http://www.w3.org/2001/XMLSchema-instance"> <ConfigurationSetType>LinuxProvisioningConfiguration</ConfigurationSetType> <HostName>myHost</HostName> <UserName>myuser</UserName> <UserPassword/> <CustomData>dGhpcyBpcyBteSB1c2VyZGF0YQ===</CustomData> <dscfg>eyJhZ2VudF9jb21tYW5kIjogWyJzdGFydCIsICJ3YWxpbnV4YWdlbnQiXX0=</dscfg> <DisableSshPasswordAuthentication>true</DisableSshPasswordAuthentication> <SSH> <PublicKeys> <PublicKey> <Fingerprint>6BE7A7C3C8A8F4B123CCA5D0C2F1BE4CA7B63ED7</Fingerprint> <Path>this-value-unused</Path> </PublicKey> </PublicKeys> </SSH> </LinuxProvisioningConfigurationSet> </wa:ProvisioningSection>
When the user launches an instance, they provide a hostname for that instance.
The hostname is provided to the instance in the
ovf-env.xml file as
Whatever value the instance provides in its DHCP request will resolve in the domain returned in the ‘search’ request.
A generic image will already have a hostname configured. The Ubuntu cloud
ubuntu as the hostname of the system, and the initial DHCP
request on eth0 is not guaranteed to occur after the datasource code has been
run. So, on first boot, that initial value will be sent in the DHCP request
and that value will resolve.
In order to make the
HostName provided in the
resolve, a DHCP request must be made with the new value.
handles this by setting the hostname in the datasource’s
via hostname $HostName, and then bouncing the interface. This
behaviour can be configured or disabled in the datasource config. See