Prerequisites : the letsencrypt CLI tool
This method allows your to generate and renew your Lets Encrypt certificates with 1 command. This is easily automatable to renew each 60 days, as advised.
You need nginx to answer on port 80 on all the domains you want a certificate for. Then you need to serve the challenge used by letsencrypt on /.well-known/acme-challenge.
Then we invoke the letsencrypt command, telling the tool to write the challenge files in the directory we used as a root in the nginx configuration.
I redirect all HTTP requests on HTTPS, so my nginx config looks like :
server {