What is metadata section during launching a VM?

asked 2017-05-16 00:15:26 -0600

ShubhamMeshram gravatar image

How excatly can I use this?

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answered 2017-05-16 00:42:38 -0600

updated 2017-05-16 00:47:32 -0600

Metadata is a set of key-value pairs that you add to an instance when you launch it and also later when it is running.

Your cloud may have a metadata catalog that allows you to give your instance certain properties, for example you might be able to request a certain CPU architecture or VM hosts with certain features like solid-state disks. When there is such a catalog, you will see available metadata items on the left of the screen. You can select the ones you want and click on the fat plus sign to copy them over to the right side, existing metadata. When the instance is launched, the scheduler will look at its metadata and find a suitable VM host.

Or you can provide your own metadata. The application running on your instance can then use it as behaviour-changing options. OpenStack doesn't impose any limitation; any key-value pair is OK. Example: Your instance runs a web server, and you provide the number of worker processes via metadata, perhaps by specifying num_workers = 10. The instance's application has to interpret this. Or you put the cloud's admin password in the metadata, so that the instance can retrieve the name of its VM host.

The instance can obtain metadata from the metadata service using the metadata API, which is AWS-compatible but also has OpenStack-specific keys.

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answered 2017-05-17 07:32:30 -0600

RHK gravatar image

updated 2017-05-17 07:32:53 -0600

Glance provides a common API to define key and value pairs that tag metadata for different types of resources (images, artifacts, volumes, flavors, aggregates, and so on). If the image that you select contains pre-defined metadata, you’ll see that in the Available metadata column.

You can create additional key and value pairs in the Custom field and click the plus sign (+) to move them to the Existing metadata list. For example, custom metadata is a parameter that you’d want to pass to the application, so it can be installed with the instance.

For more information check below links.



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Asked: 2017-05-16 00:15:26 -0600

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Last updated: May 17 '17