Config drive#
The configuration drive datasource supports the OpenStack configuration drive disk.
By default, cloud-init
always considers this source to be a
fully-fledged datasource. Instead, the typical behavior is to assume it is
really only present to provide networking information. Cloud-init
will
copy 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).
Note
See the config drive extension and metadata introduction in the public documentation for more information.
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 use a config drive:
Must be formatted with vfat filesystem.
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 use a config drive:
Must be formatted with vfat or iso9660 filesystem, or have a filesystem label of
config-2
orCONFIG-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 behaviour can be modified by keys found in the
meta.js
(version 1 only) file in the following ways.
ds-mode
#
dsmode:
values: local, net, pass
default: pass
This is what indicates if config drive is a final datasource 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 to search for other
datasources after network config.
The difference between ‘local’ and ‘net’ is that local will not require networking to be up before user-data actions are run.
instance-id
#
instance-id:
default: iid-dsconfigdrive
This is utilised 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
#
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
#
user-data:
default: None
This provides cloud-init
user data. See examples
for details of what needs to be present here.