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Automating Certificate Renewal

Overview

By default, Pi-hole v6 provides a self-signed SSL certificate, but you can automate certificate renewal with acme.sh, Cloudflare and Let's Encrypt.

This guide uses:

Prerequisites

  • Pi-hole installed and running on your system.
  • A Cloudflare account that manages your domain's DNS records.
  • Control of a registered domain (e.g., mydomain.com).

These prerequisites ensure that you can successfully request and install an SSL certificate using Cloudflare DNS validation with acme.sh.

This guide uses Cloudflare DNS and Let's Encrypt. These instructions can be adapted for any DNS provider and Certificate Authority (CA) that acme.sh supports. Simply update the --dns and --server flags accordingly when issuing your certificate.

Note: This guide assumes that acme.sh runs under the root user. The --reloadcmd contains commands that require sudo, such as removing old certificates, writing the new certificate, and restarting Pi-hole FTL. If you prefer to run acme.sh as a regular user, additional configuration is required to allow these commands to execute without a password. Methods for achieving this, such as configuring sudo rules, are beyond the scope of this article.

1. Install acme.sh as root

Run a login shell as root:

sudo -i

Install it:

curl https://get.acme.sh | sh -s email=my@example.com

Reload .bashrc to register the acme.sh alias:

source .bashrc

Verify installation:

acme.sh --version

2. Set Up Cloudflare DNS API

For DNS-based domain verification, export your Cloudflare API token:

export CF_Token="ofz...xxC"
export CF_Email="me@mydomain.com"

This allows acme.sh to create the required DNS records automatically.

3. Issue the SSL Certificate for Pi-hole

Run:

acme.sh --issue --dns dns_cf -d ns1.mydomain.com --server letsencrypt

This generates:

  • Private key: ns1.mydomain.com.key
  • Full-chain certificate: fullchain.cer (includes ns1.mydomain.com.cer + ca.cer, in that order)

You do not need these other certificate files:

  • Server certificate: ns1.mydomain.com.cer (included in fullchain.cer)
  • Intermediate CA cert: ca.cer (included in fullchain.cer)

4. Install and Apply the SSL Certificate to Pi-hole

Pi-hole requires a PEM file containing both the private key and server certificate.

Install the certificate:

acme.sh --install-cert -d ns1.mydomain.com \
  --reloadcmd "sudo rm -f /etc/pihole/tls* && \
  sudo cat fullchain.cer ns1.mydomain.com.key | sudo tee /etc/pihole/tls.pem && \\
  sudo service pihole-FTL restart"

This:

  • Deletes old certificates (/etc/pihole/tls*).
  • Creates tls.pem with both the full-chain certificate file and private key, in that order.
  • Restarts Pi-hole FTL to apply the new certificate.

5. Configure Pi-hole

To avoid domain mismatch warnings (CERTIFICATE_DOMAIN_MISMATCH), set the correct hostname:

sudo pihole-FTL --config webserver.domain 'ns1.mydomain.com'
sudo service pihole-FTL restart

Fixes:

CERTIFICATE_DOMAIN_MISMATCH SSL/TLS certificate /etc/pihole/tls.pem does not match domain pi.hole!

Notes

  • Your certificate renews automatically via acme.sh's cron job.
  • You can manually renew with:
acme.sh --renew -d ns1.mydomain.com --force
  • To check your certificate:
sudo openssl x509 -in /etc/pihole/tls.pem -text -noout