The Desktop is configured so that the X server gets its fonts from two local sources: the misc fonts directory and the local font server. The font server catalogue defines the scalable outline font directory type1 and the two bitmapped font directories 75dpi and 100dpi. All 3 directories are in /usr/X/lib/fonts. By default, the font server in UnixWare renders Type 1 fonts using Adobe Type Manager.
In vanilla X11R5, when xset fp rehash is run, only the directories in the X server's font path are re-read, not the font server directories. No utility is provided in X11R5 to request the font server to reread the directories defined in its catalogue; it does reread them, however, if sent a SIGUSR1 signal. fsfpreset is a UnixWare-specific utility that sends the needed SIGUSR1 signal to the local font server process, causing it to re-read its catalogue of available fonts.
The one argument to fsfpreset is the port number of the font server process. Using this number, fsfpreset locates the process ID of the font server process in the file /dev/X/fs.port-number.pid (this process ID is put there by the font server, fs, when it starts up), and sends that process the SIGUSR1 signal.
fsfpreset must run setuid, and with the same permissions as the fs process itself; in UnixWare this is bin, a system id.
The fontmgr process obtains the port number argument used by fsfpreset by getting the font server element out of the X server's font path; it does this for each local font server in the X server font path. (The default port number in UnixWare is 7000.)