4.6.2. FlexVolume driver example

When working with FlexVolume drivers, it is helpful to become familiar with structure of the driver.

The first command-line argument of the FlexVolume driver is always an operation name. Other parameters are specific to each operation. Most of the operations take a JavaScript Object Notation (JSON) string as a parameter. This parameter is a complete JSON string, and not the name of a file with the JSON data.

The FlexVolume driver contains:

{
	"fooServer": "192.168.0.1:1234",
        "fooVolumeName": "bar",
	"kubernetes.io/fsType": "ext4",
	"kubernetes.io/readwrite": "ro",
	"kubernetes.io/secret/<key name>": "<key value>",
	"kubernetes.io/secret/<another key name>": "<another key value>",
}

where:

OpenShift Container Platform expects JSON data on standard output of the driver. When not specified, the output describes the result of the operation.

{
	"status": "<Success/Failure/Not supported>",
	"message": "<Reason for success/failure>"
}

Exit code of the driver should be 0 for success and 1 for error.

Operations should be idempotent, which means that the mounting of an already mounted volume should result in a successful operation.