Starting with the Kilo release, 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.
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.
More information can be found at Provide user data to instances
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.
For the format of the configuration drive, Bare Metal service expects a
gzipped
and base64
encoded ISO 9660 [*] file with a config-2
label. The
ironic client
can generate a configuration drive in the expected format. Just pass a
directory path containing the files that will be injected into it via the
--config-drive
parameter of the node-set-provision-state
command,
for example:
ironic node-set-provision-state --config-drive /dir/configdrive_files $node_identifier active
When the configuration drive is enabled, the Bare Metal service will create a partition on the instance disk and write the configuration drive image onto it. The configuration drive must be mounted before use. This is performed automatically by many tools, such as cloud-init and cloudbase-init. To mount it manually on a Linux distribution that supports accessing devices by labels, simply run the following:
mkdir -p /mnt/config
mount /dev/disk/by-label/config-2 /mnt/config
If the guest OS doesn’t support accessing devices by labels, you can use
other tools such as blkid
to identify which device corresponds to
the configuration drive and mount it, for example:
CONFIG_DEV=$(blkid -t LABEL="config-2" -odevice)
mkdir -p /mnt/config
mount $CONFIG_DEV /mnt/config
[*] | A config drive could also be a data block with a VFAT filesystem on it instead of ISO 9660. But it’s unlikely that it would be needed since ISO 9660 is widely supported across operating systems. |
The configuration drive can be especially useful when used with cloud-init, but in order to use it we should follow some rules:
Cloud-init
data 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-init
has a collection of data source modules, so when
building the image with disk-image-builder we have to define
DIB_CLOUD_INIT_DATASOURCES
environment 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.
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