Setting the Root Device for Deployment

If your hardware has several hard drives, it’s highly recommended that you specify the exact device to be used during introspection and deployment as a root device. This is done by setting a root_device property on the node in Ironic. Please refer to the Ironic root device hints documentation for more details (note that the Liberty release version lacks some fields).

For example:

ironic node-update <UUID>> add properties/root_device='{"wwn": "0x4000cca77fc4dba1"}'

To remove a hint and fallback to the default behavior:

ironic node-update <UUID> remove properties/root_device

Note that the root device hints should be assigned before both introspection and deployment. After changing the root device hints you should either re-run introspection or manually fix the local_gb property for a node:

ironic node-update <UUID> add properties/local_gb=<NEW VALUE>

Where the new value is calculated as a real disk size in GiB minus 1 GiB to account for partitioning (the introspection process does this calculation automatically).

Using introspection data to find the root device

If you don’t know the information required to make a choice, you can use introspection to figure it out. First start with Introspect Nodes as usual without setting any root device hints. Then use the stored introspection data to list all disk devices:

openstack baremetal introspection data save fdf975ae-6bd7-493f-a0b9-a0a4667b8ef3 | jq '.inventory.disks'

For python-ironic-inspector-client versions older than 1.4.0 you can use the curl command instead, see Accessing Introspection Data for details.

This command will yield output similar to the following (some fields are empty for a virtual node):

[
    {
        "size": 11811160064,
        "rotational": true,
        "vendor": "0x1af4",
        "name": "/dev/vda",
        "wwn_vendor_extension": null,
        "wwn_with_extension": null,
        "model": "",
        "wwn": null,
        "serial": null
    },
    {
        "size": 11811160064,
        "rotational": true,
        "vendor": "0x1af4",
        "name": "/dev/vdb",
        "wwn_vendor_extension": null,
        "wwn_with_extension": null,
        "model": "",
        "wwn": null,
        "serial": null
    }
]

You can use all these fields, except for rotational, for the root device hints. Note that size should be converted to GiB and that name, wwn_with_extension and wwn_vendor_extension can only be used starting with the Mitaka release. Also note that the name field, while convenient, may be unreliable and change between boots.

Do not forget to re-run the introspection after setting the root device hints.