It is possible to provide some node-specific hieradata via Heat environment files and as such customize one or more settings for a specific node, regardless of the Heat ResourceGroup to which it belongs.

As a sample use case, we will distribute a node-specific disks configuration for a particular CephStorage node, which by default runs the ceph-osd service.

## Collecting the node UUID¶

The node-specific hieradata is provisioned based on the node UUID, which is hardware dependent and immutable across reboots/reinstalls.

First make sure the introspection data is available for the target node, if it isn’t one may run introspection for a particular node as described in: Introspecting a Single Node. If the undercloud.conf does not have inspection_extras = true prior to undercloud installation/upgrade and introspection, then the machine unique UUID will not be in the Ironic database.

Then extract the machine unique UUID for the target node with a command like:

openstack baremetal introspection data save NODE-ID | jq .extra.system.product.uuid


where NODE-ID is the target node Ironic UUID. The value returned by the above command will be a unique and immutable machine UUID which isn’t related to the Ironic node UUID. For the next step, we’ll assume the output was 32E87B4C-C4A7-418E-865B-191684A6883B.

## Creating the Heat environment file¶

Assuming we want to use /dev/sdc as a data disk for ceph-osd on our target node, we’ll create a yaml file, e.g. my-node-settings.yaml, with the following content depending on if either ceph-ansible (Pike and newer) or puppet-ceph (Ocata and older).

For ceph-ansible use:

parameter_defaults:
NodeDataLookup: |
{"32E87B4C-C4A7-418E-865B-191684A6883B": {"devices": ["/dev/sdc"]}}


For puppet-ceph use:

resource_registry:
OS::TripleO::CephStorageExtraConfigPre: /path/to/tripleo-heat-templates/puppet/extraconfig/pre_deploy/per_node.yaml

parameter_defaults:
NodeDataLookup: |
{"32E87B4C-C4A7-418E-865B-191684A6883B": {"ceph::profile::params::osds": {"/dev/sdc": {}}}}


In the above example we’re customizing only a single key for a single node, but the structure is that of a UUID-mapped hash so it is possible to customize multiple and different keys for multiple nodes.

Finally, add such an environment file to the deploy commandline:

openstack overcloud deploy [other overcloud deploy options] -e ~/my-node-settings.yaml