man4fs - File Systems

bootfs(4fs): bootfs — boot-time module file system
ctfs(4fs): ctfs — contract file system
dcfs(4fs): dcfs — Compression file system
dev(4fs): dev — Device name file system
devfs(4fs): devfs — Devices file system
fd(4fs): fd, stdin, stdout, stderr — file descriptor files
hsfs(4fs): hsfs — High Sierra & ISO 9660 CD-ROM file system
lofs(4fs): lofs — loopback virtual file system
objfs(4fs): objfs — Kernel object filesystem
pcfs(4fs): pcfs — FAT formatted file system
sharefs(4fs): sharefs — Kernel sharetab filesystem
smbfs(4fs): smbfs — CIFS/SMB file system
tmpfs(4fs): tmpfs — memory based file system
udfs(4fs): udfs — universal disk format file system
ufs(4fs): ufs — UFS file system