is matadata key should be "lab-logs-bucket" or any other customer key(example: custom-bucket-key) ,but i understood value should be gs (example: gs://storage-01)
The metadata functionality in GCE lets you use (almost) any key name and (almost) any key value. In that way, it’s kind of like a blank piece of paper.
But the reason you use the key name "lab-logs-bucket" and set the value in a particular ("gs://") format is because that’s what the startup script I wrote and gave you looks for. It asks the metadata service for the information (value) under that particular key name. If you used a different key, it would be like addressing your letter to "Dr. Banner" and expecting me (who is not Dr. Banner) to find and read it.
I hope this helps.