man7fs - File Systems

bootfs(7fs): bootfs - boot-time module file system
ctfs(7fs): ctfs - contract file system
dcfs(7fs): dcfs - Compression file system
dev(7fs): dev - Device name file system
devfs(7fs): devfs - Devices file system
fd(7fs): fd, stdin, stdout, stderr - file descriptor files
hsfs(7fs): hsfs - High Sierra & ISO 9660 CD-ROM file system
lofs(7fs): lofs - loopback virtual file system
objfs(7fs): objfs - Kernel object filesystem
pcfs(7fs): pcfs - FAT formatted file system
sharefs(7fs): sharefs - Kernel sharetab filesystem
smbfs(7fs): smbfs - CIFS/SMB file system
tmpfs(7fs): tmpfs - memory based file system
udfs(7fs): udfs - universal disk format file system
ufs(7fs): ufs - UFS file system