Add nerdctl system df command to analyze disk usage and layer sharing #4403

What is the problem you're trying to solve

Add nerdctl system df command to analyze disk usage and layer sharing

Describe the solution you'd like

Background

I am currently working on optimizing our container images by implementing a layered approach. The goal is to extract common components into shared layers, which can be reused across multiple services, thereby reducing the overall disk footprint.

Current Status

• In Docker, I have successfully implemented and verified this layered approach
• I can easily monitor the effectiveness using docker system df and docker system df -v, which clearly show:
  • The actual physical disk space used by images
  • Detailed information about SHARED SIZE and UNIQUE SIZE for each image
  • This helps validate that my layer optimization strategy is working as expected

Problem

Unfortunately, I cannot find an equivalent command in nerdctl. When I try to run nerdctl system df or nerdctl system df -v, these commands don't exist.

Feature Request

I would like to request adding nerdctl system df and nerdctl system df -v commands that provide similar functionality to Docker's equivalents, specifically:

1. nerdctl system df: Show a summary of disk usage by images, containers, and volumes
2. nerdctl system df -v: Show detailed information including:
   • Which images share layers
   • How much space is shared vs. unique for each image
   • Total reclamation potential

Workarounds?

In the meantime, are there any alternative commands or approaches within nerdctl or containerd that can provide similar insights into layer sharing and actual disk usage?

Thank you for considering this feature request.

Additional context

No response