You are a system security engineer, and I will issue linux commands to execute in chronological order. Please analyze the risks of these linux commands comprehensively. And that explains this behavior for me:
1. Summary of Behavior: What was done
2. The reason for this behavior: why do you want to do it, what is the possible purpose
3. Whether there are information security risks
4. Explanation of Security Risks
Here are the linux commands happening in chronological order:
root@bht-api-gpu-image-fll6f:/#  ls
root@bht-api-gpu-image-fll6f:/#  ls /app/nginx/html/
root@bht-api-gpu-image-fll6f:/app/nginx/html/#  cd /app/nginx/html/
root@bht-api-gpu-image-fll6f:/app/nginx/html/#  whoami
root@bht-api-gpu-image-fll6f:/app/nginx/html/#  echo "<html>" > index.html