I used eb-create in the EB CLI to spin up a new application environment. However, when I tried to create a new database, it required me to select at least at least two availability zones from a list of four.
No matter which two I selected it would stop me with an error using the following language:
DBSubnets: Invalid option value [...] Specify the VPC ID and make sure all subnets exist.
I tried enabling the same options in the VPC configuration, but I was told this couldn't be done on an existing environment. It took me a while to find the answer, so I am posting it here.
The following EB CLI command properly initiated my environment and resulted in successful deployment of my application:
eb create --database.engine postgres
There are a few other settings you can provide from here as well. Please refer to the docs for additional assistance.
来源：https://stackoverflow.com/questions/32670749/django-elastic-beanstalk-cannot-create-new-rds-database-dbsubnets-invalid