Proxmox: Permission-Problem with a folder in a Bind Mount Point

Love Proxmox but still have to learn a lot... I use a Bind Mount Point for my dockge-LXC on proxmox.

I used the Mount Point in my docker compose:

version: "2"

services: urbackup:

        image: uroni/urbackup-server:latest

    container_name: urbackup

    restart: unless-stopped

    environment:

      - PUID=1000 # Enter the UID of the user who should own the files here

      - PGID=1000 # Enter the GID of the user who should own the files here

      - TZ=Europe/Berlin # Enter your timezone

    volumes:

      - /media/urbackups/data:/var/urbackup

      - /media/urbackups/storage:/backups

      # Uncomment the next line if you want to bind-mount the www-folder

      #- /path/to/wwwfolder:/usr/share/urbackup

    network_mode: host

    # Activate the following two lines for BTRFS support

    cap_add:

      - SYS_ADMIN


  

networks: {}

Now i geht this permission-error:

urbackup | usermod: no changes

urbackup | chown: changing ownership of '/backups': Operation not permitted

I guess it has to do with the PUID, but i do not know the PUID.

I read that it has to be the user "urbackup" but also in the docker?

The mounted folders are both 777.

Can you help me?