How to add a subdomain to an existing certificate using certbot

You're most likely reading this because you already have a Let's Encrypt certificate issued using certbot for a domain.

If you want to create a new certificate, have a look at this guide instead.

In our case, we already had SSL certificates covering these domains:

• https://example.ca

• https://www.example.ca

I have a directory on my server called "staging" that I want to link with https://staging.example.ca

We add our new subdomain with the certbot command and the --expand flag.

sudo certbot -d staging.example.ca --expand

We can then list all certbot domains and confirm that the subdomain has been added successfully.

sudo certbot certificates

Saving debug log to /var/log/letsencrypt/letsencrypt.log - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - Found the following certs: Certificate Name: example.ca Domains: example.ca Expiry Date: 2022-07-11 02:01:35+00:00 (VALID: 62 days) Certificate Path: /etc/letsencrypt/live/example.ca/fullchain.pem Private Key Path: /etc/letsencrypt/live/example.ca/privkey.pem Certificate Name: www.example.ca Domains: www.example.ca Expiry Date: 2022-07-16 02:46:28+00:00 (VALID: 68 days) Certificate Path: /etc/letsencrypt/live/www.example.ca/fullchain.pem Private Key Path: /etc/letsencrypt/live/www.example.ca/privkey.pem Certificate Name: staging.example.ca Domains: staging.example.ca Expiry Date: 2022-07-20 19:19:31+00:00 (VALID: 90 days) Certificate Path: /etc/letsencrypt/live/staging.example.ca/fullchain.pem Private Key Path: /etc/letsencrypt/live/staging.example.ca/privkey.pem - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

Check out the full guide on setting up a subdomain using the same Apache web server or the one for NGINX as well.

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