Checklists for software errors, setup, and tool workflows.

1. Reproduce

2. Isolate

3. Apply

4. Verify

Latest checklists

If you see a Cloudflare 521 error, it means Cloudflare can't establish a TCP connection to yo...

When you see fatal: unable to access 'https://...': SSL certificate problem: unable...

Setup Cloudflare Origin Certificate for Nginx
If you use Cloudflare as a reverse proxy, enabling HTTPS between Cloudflare and your Nginx server...

Fix Nginx Upstream Connection Refused in Docker
You have Nginx running, either on the host or in a container, proxying to another Docker containe...

Fix 'Python Command Not Found' in Git Bash on Windows
When running Python in Git Bash on Windows, you may see bash: python: command not found

Fix Git 'index.lock file exists' Error
If you see fatal: Unable to create 'path/.git/index.lock': File exists. when...