You should have a file named something containing "RC" in the directory which should be created when you run DevStack, this file contains some variables that is set for authentication against Keystone, for example the OS_USERNAME environment variable is one of them.
You can either "source" this file and then run your commands or you can provide the python-cinderclient (the Cinder CLI client) with parameters for the credentials, for example the --os-username.
Example would be
cat adminrc
export OS_TENANT_NAME=admin
export OS_USERNAME=admin
export OS_PASSWORD=adminpasswordhere
export OS_AUTH_URL=http://127.0.0.1:35357/v2.0
export OS_VOLUME_API_VERSION=2
source adminrc
cinder list
The reason I set OS_VOLUME_API_VERSION to version 2 is simply because version 1 is or is being deprecated so it's disabled on our cloud (OpenStack Kilo).
Best regards