Swift is the object storage service in OpenStack.
There is Amazon S3 API compatibility in Swift and the only thing you need to do is to create ec2 credentials in OpenStack.
Using the OpenStack CLI, run the following command
openstack ec2 credentials create
The S3 region must be “us-east-1” for compatibility with “AWS Signature Version 4”.
Here is a sample s3cmd config
access_key = 00000000000000000000000000000
secret_key = 00000000000000000000000000000
host_base = swift.elastx.cloud
host_bucket = swift.elastx.cloud
use_https = True
bucket_location = us-east-1