Setup of a ssl certificate with let’s encrypt
last modified: 2018-10-18
I use Debian, version 8.7 (why?)
Vi is used as a text editor in the following
For users, no SSL shows as "http://" in front of a website address, and with SSL it shows as "https://"
"https" means that the connection between the user and the website is encrypted. It is useful for:
human to machine communication: https keeps the email you write private on its way to gmail.com
machine to machine communication: the api secret used by a machine to authenticate in a GET or PUT request is kept private.
Installing the Certbot by Let’s Encrypt
The "certbot" is the EFF’s latest package to let your server use let’s encrypt capabilities.
So, let’s install the certbot:
sudo vi /etc/apt/sources.list.d/sources.list
In this file, add a line
deb http://ftp.debian.org/debian jessie-backports main
sudo apt-get update
sudo apt-get install certbot -t jessie-backports
make sure your domain already points to the IP of your server (with a DNS record)
make sure your firewall allows port 443 (with ufw: just do sudo ufw allow 443).
→ in the interactive window, choose "standalone". Follow the instructions.
That’s it. Certificates get installed at:
Automatic renewal of SSL certificates
Certificates expire after 90 days, so renewing them manually and regularly is a pain.
Thanks to certbot, they will renew themselves automatically, you don’t need to add any script. Just check that it indeed works:
certbot renew --dry-run
(this will not renew them, but just simulate the action)
This command is useful because you may realize that your port 443 needs to be open for the renewal to succeed. With Nginx or another reverse proxy running, 443 is already in use so the the renewal will fail.
Solution for nginx:
with root privileges, edit a crontab:
Add the following line:
@monthly certbot renew --pre-hook "sudo systemctl stop nginx" --post-hook "sudo systemctl start nginx"
This will test every month the need to renew certificates. Only when there is a need, nginx will be stopped before then restarted after the operation.
Author of this tutorial: Clement Levallois
All resources on linux security: https://seinecle.github.io/linux-security-tutorials/