In the absence of this file in any given directory, and thus by default, the "umsdos" filesystem driver provides the same semantics as the "msdos" filesystem driver does for the directory: only 8.3 filenames and no extra Unix file semantics. To enable the "umsdos" driver's extra abilities, it is necessary to create that file in the directory and synchronize its internal data with the normal FAT data for any existing entries already in the directory. This is done with a tool called codice_17.