Disk Quota with Systemd Nspawn

BTRFS quota is done on top of subvolumes. One possible approach, then is to create subvolumes and set their quotas before binding to the container.

I hope the links below can help you:

  1. https://wiki.archlinux.org/index.php/btrfs
  2. https://wiki.archlinux.org/index.php/User:I2Oc9/Btrfs_subvolumes

This is not as simple as having CPUQuota = 10% on your .service file but should work. You can wrap this warm up in a setup script to make it smoother and reduce code duplication.