Certbot

certbot^[1] is a fully-featured, extensible client for the Let’s Encrypt CA (or any other CA that speaks the ACME protocol defined in 2015-2016) that can automate the tasks of obtaining certificates and configuring webservers to use them. This client runs on Unix-based operating systems.

apt install certbot

Ubuntu:

Binaries: certbot and letscrypt
Configuration files: /etc/letsencrypt
Renewals configuration: /etc/cron.d/certbot

Examples

certbot -d YOUR_DOMAIN_NAME.com --manual --preferred-challenges dns certonly

To request a certificate:

Stop your webserver: systemctl stop nginx
certbot certonly --standalone --preferred-challenges http -d YOUR_DOMAIN_NAME.com

Client with the currently selected authenticator does not support any combination of challenges that will satisfy the CA. You may need to use an authenticator plugin that can do challenges over DNS.

certbot certonly --standalone --agree-tos --preferred-challenges dns -d *.YOUR_DOMAIN_NAME.com (You will be asked for information)

None of the preferred challenges are supported by the selected plugin

nginx.conf

ssl_certificate /etc/letsencrypt/live/www.example.com/fullchain.pem;

ssl_certificate_key /etc/letsencrypt/live/www.example.com/privkey.pem;

certbot certonly --standalone

certbot --nginx
Saving debug log to /var/log/letsencrypt/letsencrypt.log
The requested nginx plugin does not appear to be installed

certbot certificates
Saving debug log to /var/log/letsencrypt/letsencrypt.log

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No certs found.
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certbot renew
Saving debug log to /var/log/letsencrypt/letsencrypt.log

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No renewals were attempted.
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certbot renew --force-renewal

certbot delete --cert-name YOUR_CERT_NAME
Saving debug log to /var/log/letsencrypt/letsencrypt.log

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Deleted all files relating to certificate YOUR_CERT_NAME.
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Changing a Certificdate's Domain^[2]: certbot certonly --cert-name example.com -d example.org,www.example.org
Automated renewals: systemctl list-timers