Enabling the configuration drive (configdrive)¶
The Bare Metal service supports exposing a configuration drive image to the instances.
The configuration drive is used to store instance-specific metadata and is present to
the instance as a disk partition labeled
config-2. The configuration drive has
a maximum size of 64MB. One use case for using the configuration drive is to
expose a networking configuration when you do not use DHCP to assign IP
addresses to instances.
The configuration drive is usually used in conjunction with the Compute service, but the Bare Metal service also offers a standalone way of using it. The following sections will describe both methods.
When used with Compute service¶
To enable the configuration drive for a specific request, pass
--config-drive true parameter to the nova boot command, for example:
nova boot --config-drive true --flavor baremetal --image test-image instance-1
It’s also possible to enable the configuration drive automatically on
all instances by configuring the
OpenStack Compute service to always
create a configuration drive by setting the following option in the
/etc/nova/nova.conf file, for example:
[DEFAULT] ... force_config_drive=True
In some cases, you may wish to pass a user customized script when deploying an instance.
To do this, pass
--user-data /path/to/file to the nova boot command.
When used standalone¶
When used without the Compute service, the operator needs to create a configuration drive and provide the file or HTTP URL to the Bare Metal service. See Deploying with a config drive for details.
Configuration drive storage in an object store¶
Under normal circumstances, the configuration drive can be stored in the Bare Metal service when the size is less than 64KB. Optionally, if the size is larger than 64KB there is support to store it in a swift endpoint. Both swift and radosgw use swift-style APIs.
The following option in
/etc/ironic/ironic.conf enables swift as an object
store backend to store config drive. This uses the Identity service to
establish a session between the Bare Metal service and the
Object Storage service.
[deploy] ... configdrive_use_object_store = True
Use the following options in
/etc/ironic/ironic.conf to enable radosgw.
Credentials in the swift section are needed because radosgw will not use the
Identity service and relies on radosgw’s username and password authentication
[deploy] ... configdrive_use_object_store = True [swift] ... username = USERNAME password = PASSWORD auth_url = http://RADOSGW_IP:8000/auth/v1
If the Direct deploy is being used, edit
to store the instance images in respective object store (radosgw or swift)
[glance_store] ... swift_store_user = USERNAME swift_store_key = PASSWORD swift_store_auth_address = http://RADOSGW_OR_SWIFT_IP:PORT/auth/v1
Accessing the configuration drive data¶
When the configuration drive is enabled, the Bare Metal service will create a partition on the instance disk and write the configuration drive image onto it. The configuration drive must be mounted before use. This is performed automatically by many tools, such as cloud-init and cloudbase-init. To mount it manually on a Linux distribution that supports accessing devices by labels, simply run the following:
mkdir -p /mnt/config mount /dev/disk/by-label/config-2 /mnt/config
If the guest OS doesn’t support accessing devices by labels, you can use
other tools such as
blkid to identify which device corresponds to
the configuration drive and mount it, for example:
CONFIG_DEV=$(blkid -t LABEL="config-2" -odevice) mkdir -p /mnt/config mount $CONFIG_DEV /mnt/config
The configuration drive can be especially useful when used with cloud-init, but in order to use it we should follow some rules:
Cloud-initdata should be organized in the expected format.
Since the Bare Metal service uses a disk partition as the configuration drive, it will only work with cloud-init version >= 0.7.5.
Cloud-inithas a collection of data source modules, so when building the image with disk-image-builder we have to define
DIB_CLOUD_INIT_DATASOURCESenvironment variable and set the appropriate sources to enable the configuration drive, for example:
DIB_CLOUD_INIT_DATASOURCES="ConfigDrive, OpenStack" disk-image-create -o fedora-cloud-image fedora baremetal
For more information see how to configure cloud-init data sources.