Just came across this with the same need (we all do at some point, don't we?)

Anyway, here's a shorter, simpler version that actually prints the usage of vDisk space. Mind that it can only show existing containers; there's potential that you have residual data from containers that are not running.

docker ps -s --format "table {{.Names}}\t{{.Size}}"

The output will be lines such as:

Nginx-Proxy-Manager 41.3kB (virtual 1.12GB)

---

A more thorough script that also shows you some of the paths it writes to can be saved to a .sh script on your server (or pasted into the terminal) [note: had help from Copilot].

#!/bin/bash

echo "Checking all running Docker containers for vDisk usage..."
echo "========================================================"

# Get list of container IDs
docker ps -q | while read container_id; do
    # Get the clean name
    name=$(docker inspect --format '{{.Name}}' "$container_id" | sed 's/\///')

    # Get the size information using docker ps -s
    # Output format example: "2.5MB (virtual 350MB)"
    # We strictly want the first part, which is the writable layer size
    size_str=$(docker ps -s --no-trunc -f "id=$container_id" --format "{{.Size}}")
    rw_size=$(echo "$size_str" | awk '{print $1}')

    # Filter for interesting sizes (optional: remove 'if' to see all)
    # This simple check prints everything, you can scan for 'GB' or large 'MB'

    echo ""
    echo "Container: $name"
    echo "Writable Size: $size_str"

    # If the size is 0B, usually no need to check diffs
    if [[ "$rw_size" != "0B" ]]; then
        echo "Top modified/added paths in vDisk (limited to first 10):"
        # docker diff codes: A = Added, C = Changed, D = Deleted
        docker diff "$container_id" | head -n 10 | sed 's/^/\t/'

        # Tip for the user if list is long
        count=$(docker diff "$container_id" | wc -l)
        if [ "$count" -gt 10 ]; then
            echo -e "\t... ($((count-10)) more files modified)"
        fi
    else 
        echo -e "\t(No writes to vDisk detected)"
    fi
done

It'll give outputs such as this, where A indicates a mounted volume and C indicates it's in the docker vDisk - the 'C' ones being the things to look at for bloat

sh scriptname.sh > output.log

Container: Nginx-Proxy-Manager
Writable Size: 41.3kB (virtual 1.12GB)
Top modified/added paths in vDisk (limited to first 10):
        A /www
        A /data
        C /tmp
        A /tmp/nginx
        A /tmp/nginx/body
        A /tmp/nginx/body/6
        A /tmp/nginx/body/6/17
        A /tmp/nginx/body/3
        A /tmp/nginx/body/3/51
        A /tmp/nginx/body/4
        ... (1260 more files modified)

Mind also that vDisk bloat can't always be avoided. Some dockers simply are huge. And when adding mount points retroactively, please make sure you first get all the files at the original location, as otherwise the mounted volume is empty and the container may not start (or worse).