lego --email="foo@bar.com" --domains="example.com" --dns="route53" run
```
### Obtain a certificate given a certificate signing request (CSR) generated by something else
```bash
lego --email="foo@bar.com" --http --csr=/path/to/csr.pem run
```
(lego will infer the domains to be validated based on the contents of the CSR, so make sure the CSR's Common Name and optional SubjectAltNames are set correctly.)