Checklists for software errors, setup, and tool workflows.

1. Reproduce

2. Isolate

3. Apply

4. Verify

Latest checklists

When you try to merge two branches that have no common commit history, Git refuses with fat...

Git index.lock File Exists Even After Deleting: Fixes
You delete the .git/index.lock file, but Git still says it exists. This can happen d...

Fix Nginx Configuration Test Failed: Duplicate Listen Error
When running nginx -t to test your configuration, you may see an error like "...

How to Change npm Directory to Avoid Permission Denied
If you've seen "EACCES: permission denied" when running npm install -g, ...

Fix Cloudflare 521 Error Due to Server Overload
You see a Cloudflare 521 error page. The message says the web server is down. Often, this means y...

Fix Nginx Redirect Loop After SSL Setup
You've set up SSL on your Nginx server, but now visitors get stuck in a redirect loop—HTTP→HT...