Abiquo stores some information in VMs as metadata and allows users to store custom metadata too. To access metadata, use the link with the "rel" value of "metadata" in the VM.
Writing metadata will overwriteALL existing metadata, so to obtain a base object to modify, retrieve the existing metadata in the appropriate format. Abiquo recommends JSON format.
Note: Do not use a conversion tool to convert between JSON and XML format because this may produce an incompatible data transfer object.
For the metadata attribute or object, Abiquo has the reserved keys that are described in the following table.
Metadata type
Reserved keys
Description
Chef
chef
Users enter Chef recipe attributes as JSON in the UI, in the VM dialog on the Chef / Attributes tab
Abiquo stores the recipe attributes that you enter in JSON format as an escaped string under the chef key
Bootstrap script
startup-script
Cloud-config for use by cloud-init
Users enter Startup script in the UI, on the VM dialog on the Bootstrap script tab
Metrics
monitoring-metrics
Names of the metrics available for the VM – useful for accessing metrics via API
Custom
Append custom metadata to the existing metadata
Do not use the Abiquo reserved metadata keys
VM metadata tutorial
This tutorial will show you how to retrieve and update metadata to add a startup script to your VM via API.
To work through this tutorial, you will need:
A VM that is not deployed (or a VM that is powered off)
This tutorial uses an example VM that is not deployed
User with privileges to work with VMs and Manage virtual machine backup configuration (VAPP_MANAGE_BACKUP) because backups previously used metadata
Optional: a monitoring server and a user with the privileges to Manage virtual machine metrics (USERS_ENABLE_DISABLE_VM_METRICS)
Get the VM and the metadata link
To get started, use a query to retrieve all of your VMs from the cloud and select the desired VM. Here we are filtering the VMs using the "vmlabel" parameter to select the one that has a text string (in this case "metadata") as part of the name, which is an easy way to find a VM that you have located in the UI.
GET all virtual machines in the cloud, filtering by name
There is also a metadata attribute in the VM with a null value, but the correct way to access metadata is using the metadata link.
Retrieve existing VM metadata
Use the VM metadata link from the step above to retrieve any existing metadata.
When there is no metadata, the query returns a 200 status code, and a data object with an empty links list and a null metadata attribute.
Optionally enable monitoring, select metrics, and retrieve metadata again
To move ahead quickly, in the UI enable "Fetch metrics" and don't select any metrics to retrieve. Then retrieve metadata again using the same GET request as in the previous step.
The metadata object will now have an empty monitoring-metrics list.
Now select one or more metrics to retrieve. In the UI we selected two of the built-in metrics from a KVM hypervisor and performed the GET request again.
Prepare a metadata object with a VM startup script
The platform will store the VM startup script in the VM metadata under the "startup-script" key.
Abiquo supports cloud-config scripts with cloud-init templates in private cloud, and in public cloud.
To add the startup script to the JSON object, first escape any special characters, such as quotation marks, in the startup script.
So for example, we have the following script for use with a cloud-init template on a Linux system.
Disclaimer: this is a sample script for illustrative purposes only. Please see cloud-init documentation to find out how this script works.
And after you escape the special characters it will look like this:
Tip: you can use a JSON string escape/unescape tool to create this format.
Add the startup script to the metadata object with the "startup-script" key. Don't forget to add a comma after the previous object. For our example, after adding the startup script, the metadata object looked like this:
Update VM metadata
To update the VM metadata, perform a PUT request to the metadata link.
In this case, the requestpayload.json file should contain the JSON object from the previous step.
Metadata requestpayload.json object
If the request is successful, it will return a status code of 200 and the updated metadata object.
And that's all!
Access metadata as part of the VM
Here we made a GET request to obtain the VM object and we removed the links to make it easier to read. Here, the metadata object is part of the VM but the links list is not shown.
Although you can read the metadata here, the most correct and convenient way to work with VM metadata is using the metadata link as described in the previous steps.
Delete metadata
If you ever need to delete the VM metadata, just send a DELETE request to the metadata link. But remember that this request will delete ALL metadata, leaving just the empty links list and the null metadata key, as shown in the first example when we retrieved the empty metadata object.
Related links
Some API references about working with VM metadata: