My site is on a DigitalOcean machine, and uses nginx. So I mostly followed The helpful howto on DigitalOcean itself.

Install the certificate

The summary is:

sudo git clone https://github.com/letsencrypt/letsencrypt /opt/letsencrypt

Add this to server section in nginx config file:

location ~ /.well-known {
    allow all;
}

Then reload nginx and get the certificates:

sudo service nginx reload

cd /opt/letsencrypt
./letsencrypt-auto certonly -a webroot -w /path/to/root/of/html/files -d jeffroush.com -d www.jeffroush.com -d curlydogsystems.com -d www.curlydogsystems.com

Generate a strong Diffie-Hellman group:

sudo openssl dhparam -out /etc/ssl/certs/dhparam.pem 2048

Delete these from nginx config file:

listen 80 default_server;
listen [::]:80 default_server ipv6only=on;

Add these to the server block of the nginx config file:

listen 443 ssl;

server_name example.com www.example.com;

ssl_certificate /etc/letsencrypt/live/example.com/fullchain.pem;
ssl_certificate_key /etc/letsencrypt/live/example.com/privkey.pem;

ssl_protocols TLSv1 TLSv1.1 TLSv1.2;
ssl_prefer_server_ciphers on;
ssl_dhparam /etc/ssl/certs/dhparam.pem;
ssl_ciphers 'ECDHE-RSA-AES128-GCM-SHA256:ECDHE-ECDSA-AES128-GCM-SHA256:ECDHE-RSA-AES256-GCM-SHA384:ECDHE-ECDSA-AES256-GCM-SHA384:DHE-RSA-AES128-GCM-SHA256:DHE-DSS-AES128-GCM-SHA256:kEDH+AESGCM:ECDHE-RSA-AES128-SHA256:ECDHE-ECDSA-AES128-SHA256:ECDHE-RSA-AES128-SHA:ECDHE-ECDSA-AES128-SHA:ECDHE-RSA-AES256-SHA384:ECDHE-ECDSA-AES256-SHA384:ECDHE-RSA-AES256-SHA:ECDHE-ECDSA-AES256-SHA:DHE-RSA-AES128-SHA256:DHE-RSA-AES128-SHA:DHE-DSS-AES128-SHA256:DHE-RSA-AES256-SHA256:DHE-DSS-AES256-SHA:DHE-RSA-AES256-SHA:AES128-GCM-SHA256:AES256-GCM-SHA384:AES128-SHA256:AES256-SHA256:AES128-SHA:AES256-SHA:AES:CAMELLIA:DES-CBC3-SHA:!aNULL:!eNULL:!EXPORT:!DES:!RC4:!MD5:!PSK:!aECDH:!EDH-DSS-DES-CBC3-SHA:!EDH-RSA-DES-CBC3-SHA:!KRB5-DES-CBC3-SHA';
ssl_session_timeout 1d;
ssl_session_cache shared:SSL:50m;
ssl_stapling on;
ssl_stapling_verify on;
add_header Strict-Transport-Security max-age=15768000;

Then add these outside the server block to redirect http requests to https:

server {
    listen 80;
    server_name example.com www.example.com;
    return 301 https://$host$request_uri;
}

Then reload nginx:

sudo service nginx reload

If you’ve typed something wrong, and nginx doesn’t restart, have it check the config file:

sudo nginx -t

Auto renew the certificate

sudo crontab -e

Add these lines to crontab:

30 2 * * 1 /opt/letsencrypt/letsencrypt-auto renew >> /var/log/le-renew.log
35 2 * * 1 /etc/init.d/nginx reload