bchanot-cv/.claude/memory/learnings.md

---

type: learnings_registry entry_prefix: LRN schema: id: LRN-XXX date: YYYY-MM-DD pattern: string (what was observed, abstracted) context: string (where/when it happened - concrete) future_application: string (when to recall this) rules:

• Capture learnings that apply beyond the current task.
• Abstract from the incident - the pattern is what is reusable, not the one-shot fact.
• Link to source (commit, file, PR) when possible. ---

Learnings registry (LRN)

Index

ID	Date	Pattern	Applies to
LRN-001	2026-05-15	certbot --nginx matches server_name, not filename	nginx + certbot on multi-site VPS

---

LRN-001 — certbot --nginx matches server_name, not filename

• Date: 2026-05-15
• Pattern: certbot install --cert-name X (and certbot --nginx -d X) locates the target vhost by scanning every server_name directive in active nginx configs. The filename in sites-available/ is irrelevant. A file named X.conf with server_name Y; inside will NOT be picked up for domain X.
• Context: /etc/nginx/sites-available/bchanot.fr existed and was symlinked into sites-enabled/, but its body still contained server_name autreprojet.fr www.autreprojet.fr; — a copy-paste leftover from a previous project. Certbot returned Could not automatically find a matching server block for bchanot.fr.
• Future application: Before running certbot on a multi-site VPS, grep -n "server_name" /etc/nginx/sites-enabled/* — confirm the target domain is actually declared inside, not just present in the filename. Same logic applies when troubleshooting "why is nginx serving the wrong site" — match by server_name, never by filename.