Checklists for software errors, setup, and tool workflows.

How to Fix Git Detached HEAD State and Undo Changes

You run git status and see something like "HEAD detached at abc123". This ha...

Fix Nginx 'upstream connection refused' When Talking to PHP-FPM

You're seeing upstream connection refused in your Nginx error log, and your site...

How to Fix Nginx Redirect Loop in Server Block

You set up a server block in Nginx, but now the browser keeps redirecting—http to https, or www t...

Fix 'package.json Not Found' After Cloning a Repository

Symptom

You clone a repository from GitHub (or another remote), change into the directory...

How to Fix Cloudflare 522 Error: Origin Server Timeout

If you see a Cloudflare 522 error, it means your origin server didn't respond in time. This u...

Fix Node.js Out of Memory When Building React Apps

When building a React app, you might see a fatal error like FATAL ERROR: Ineffective mark-c...