If you are running Boundary v0.1.1, try the following:
$ boundary authenticate password -auth-method-id=ampw_1234567890 \
-login-name=admin -password=password \
-keyring-type=none -format=json | jq -r ".token" > boundary_token.txt
$ export BOUNDARY_TOKEN=$(cat boundary_token.txt)
(Note: For v0.1.0, it’s -token-name instead of -keyring-type.)
Refer to the Authenticate with Boundary section in the Start a Development Environment tutorial.