Q: Set up auto-renewal (/etc/cron.d) ? what does --dry-run mean ? sudo certbot renew --dry-run
You've asked about setting up auto-renewal for Certbot and what the --dry-run flag does.
Certbot's official packages from repositories like EPEL on CentOS/RHEL or the official PPA on Ubuntu/Debian typically handle auto-renewal for you automatically. When you install Certbot, it usually creates a cron job or a systemd timer that runs twice a day to check for certificates that need renewal.
You can verify this by checking for the presence of a file in /etc/cron.d/certbot or /etc/cron.daily/certbot. This file contains the command that Certbot will use to check for and renew certificates.