Good Info:
https://www.interserver.net/tips/kb/install-lets-encrypt-cpanel-whm-server/
https://lowendtalk.com/discussion/106071/installing-free-ssl-for-server-hostname-using-letsencrypt
Login to the server via ssh andlLet’s run the following command to install Let’s Encrypt provider:
/scripts/install_lets_encrypt_autossl_provider
Once you have installed Let’s Encrypt provider, change auto SSL provider to Let’s Encrypt from cPanel (powered by Sectigo).
Login to WHM >> Manage AutoSSL.
Select Let’s Encrypt from cPanel (powered by Sectigo). Check the “I agree to these terms of service.”, and the “Recreate my current registration with “Let’s Encrypt”.
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Install Self-Signed Certificate to Hostname.
Login to WHM as a root user. Go to “Service Configuration”.
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Then select the following services and click on “Browse Certificate”. Calendar, cPanel, WebDisk, Webmail, and WHM Services, Dovecot Mail Server, Exim (SMTP) Server, FTP Server.
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Select hostname and click on “Use Certificate”.
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Then click on “Install”.
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Restart cpsrvd
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Replace Self Signed Certificates with Valid Let’s Encrypt Certificates.
Once you have installed the self-signed certificate, run the following command to check SSL certificates
/usr/local/cpanel/bin/checkallsslcerts --verbose
We can see the SSL CRT’s have been requested for your services. The hostname for the SSL CRT will be with one that is currently defined in cPanel:
# whmapi1 gethostname|grep hostname:
hostname: server1.hostname.com
While the process is not always this fast, after a few moments, we can see the SSL CRT’s are ready for install.
Then re-ran the ‘/usr/local/cpanel/bin/checkallsslcerts –verbose’ command which would have been ran at maintenance time. You may verify at WHM > Service Configuration > Manage Service SSL Certificates.
You can verify SSL installation by running https://server1.hostname.com:2087