--- name: certbot description: Expert Certbot SSL/TLS certificate assistance covering Let's Encrypt, ACME DNS/HTTP validation, and auto-renewal. Use when provisioning SSL certificates, setting up HTTPS, or troubleshooting cert renewals. --- # Certbot Certbot is a free, open-source software tool for automatically using Let's Encrypt certificates on manually-administrated websites to enable HTTPS. ## When to Use - **Automated SSL/TLS Certificate Issuance**: Provisioning free, trusted Let's Encrypt certificates for web servers. - **Automatic Certificate Renewal**: Configuring cron or systemd timers to renew expiring certificates without downtime. - **Wildcard Certificate Provisioning**: Generating wildcard certificates (`*.example.com`) via automated DNS-01 challenges. - **Web Server Configuration Automation**: Automatically configuring HTTPS directives, ciphers, and redirects in Nginx and Apache. ## Quick Start ```bash sudo snap install --classic certbot sudo ln -s /snap/bin/certbot /usr/bin/certbot # Auto-configure Nginx sudo certbot --nginx ``` ## Core Concepts ### Automated Certificate Management Environment (ACME) Certbot proves domain ownership to the Let's Encrypt Certificate Authority through challenge-response protocols: ```text [ Web Server (Certbot) ] ──1. Request Certificate──→ [ Let's Encrypt CA ] ←─2. Challenge (HTTP-01)─── [ Let's Encrypt CA ] ──3. Fetch /.well-known/acme-challenge/──→ [ Web Server ] [ Let's Encrypt CA ] ──4. Issue Signed Certificate (90 Days)─────────→ [ Web Server ] ``` ### HTTP-01 vs DNS-01 Challenge Types - **HTTP-01**: Serves a challenge file over port 80 at `/.well-known/acme-challenge/`. Simple, but cannot issue wildcard certificates. - **DNS-01**: Creates a TXT record `_acme-challenge.example.com`. Required for wildcard certificates and internal/private servers: ```bash # Issue Wildcard Certificate via Cloudflare DNS-01 Challenge certbot certonly \ --dns-cloudflare \ --dns-cloudflare-credentials ~/.secrets/cloudflare.ini \ -d "example.com" -d "*.example.com" ``` ### Non-Interactive Standalone Mode Spins up a temporary standalone web server to validate domain control on machines without existing web servers: ```bash certbot certonly --standalone -d api.example.com --non-interactive --agree-tos -m admin@example.com ``` ## Common Patterns ### Automated Nginx Wildcard Certificate via DNS Challenge **Problem**: HTTP-01 challenges fail on private services, firewalled servers, or wildcard subdomains. **Solution**: Use the DNS-01 validation plugin for automated wildcard provisioning: ```bash certbot certonly \ --dns-cloudflare \ --dns-cloudflare-credentials /etc/letsencrypt/cloudflare.ini \ -d "*.example.com" -d "example.com" \ --agree-tos --email security@example.com --non-interactive ``` ## Best Practices **Do**: - Test with `--dry-run` First: Always test issuance and renewal against the Let's Encrypt staging environment to avoid hitting production rate limits. - Automate Service Reloads with Deploy Hooks: Use `--deploy-hook "systemctl reload nginx"` so web servers reload new certificates upon renewal. - Retain Port 80 Open: Keep HTTP port 80 open to allow HTTP-01 renewal challenges to succeed smoothly. - Monitor Expiration Dates with Prometheus / Datadog: Set up alerts if certificates have fewer than 20 days remaining. **Don't**: - Forget to configure renewal timers: Verify that `systemctl list-timers | grep certbot` is active and running twice daily. - Hardcode DNS provider API tokens with global write access: Restrict cloud DNS API tokens to modify only the `_acme-challenge` TXT records. - Delete `/etc/letsencrypt/` files manually: Use `certbot delete --cert-name ` to remove decommissioned certificate configs. ## Troubleshooting | Error | Cause | Solution | | :----------- | :----------------- | :------------------------------------------------------------ | | `Timeout` | Port 80 blocked. | Open Firewall/Security Group for Port 80 (HTTP-01 challenge). | | `Rate Limit` | Too many failures. | Wait 1 hour or use `--test-cert`. | ## References - [Certbot Instructions](https://certbot.eff.org/) --- Source attribution: G1Joshi Original project: https://github.com/G1Joshi/Agent-Skills/blob/6a74cf03a8a86dc7d993ead3091b41123dbd0181/skills/security/certbot/SKILL.md License: MIT License information: https://opensource.org/license/mit Original upstream instructions; downloaded from Dave AI. ## Upstream license notice MIT License Copyright (c) 2026 G1Joshi Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions: The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software. THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. # Dave AI resource metadata Creator / publisher: G1Joshi Original project: https://github.com/G1Joshi/Agent-Skills/blob/6a74cf03a8a86dc7d993ead3091b41123dbd0181/skills/security/certbot/SKILL.md Attribution basis: Source repository record Fields of work: Development & Engineering, Operations Roles: Backend Developer, DevOps / SRE, IT Operations Specialties: DevOps Tools: Letsencrypt Country applicability: Country not specified Classification basis: Source catalog labels Instruction SHA-256: 6cd7b2ee244e882735beeba561f4caabfb98271c63e02ae0cbd60fa35fbfd9a5