fusequota is a FUSE file system layer that is mounted over a directory so that file operations on the new mount point are checked to ensure they do not violate the size restrictions the administrator has set. It aims to be a simple, modular extension to traditional user- and directory-based quotas. A situation where directory-based quotas would be desired could be in hosting virtual mailboxes, for example, where users may not correspond to system users and data is partitioned into directories anyway.