initial docs

Author: jbasney

README.md

@@ -1,2 +1,23 @@
 # letsencrypt-certificates
-install Let's Encrypt CA certificates in /etc/grid-security/certificates
+You get user certificates from [CILogon](https://cilogon.org/) but you also need host certificates.
+You looked over the list of [IGTF](https://igtf.net) CAs but they don't meet your needs.
+Why not use the [Let's Encrypt CA](https://letsencrypt.org/)?
+How do you set up `/etc/grid-security` for the Let's Encrypt CA?
+
+## Getting your host certificate
+Follow the Let's Encrypt [Getting Started](https://letsencrypt.org/getting-started/) guide.
+
+## Setting up /etc/grid-security/host*.pem
+```
+ln -s /etc/letsencrypt/live/*/cert.pem /etc/grid-security/hostcert.pem
+ln -s /etc/letsencrypt/live/*/privkey.pem /etc/grid-security/hostkey.pem
+chmod 0600 /etc/letsencrypt/archive/*/privkey*.pem # ugh!
+```
+
+## Setting up /etc/grid-security/certificates
+```
+git clone https://github.com/cilogon/letsencrypt-certificates.git
+cd letsencrypt-certificates/
+make
+sudo make install
+```