https://www.freebsd.org/doc/handbook/disk-organization.html

disk organization
--
file: filename is case sensitive readme.txt README.txt differ
dir: directory can be empty
file under dir: foo/bar/read.txt (where / mean under)
root: directory top level directory /

partiton: 
 diff than MSDOS, each partition is identified by a letter from a to h
 each partition can contain only one file system

partiton name:
 a root fs
 b swap

slice: disk divided into slices (like windows partiton) from 1 to 4
extented slice: number from 5 (logical slice under physical slice)
 da0s1 :the first slice on the first SCSI disk
 ada0s5 :the first extended slice on the first SATA disk
 da0a :a partition on the first da drive
 ada1s3e :fifth partition in the third slice of the second SATA disk

file system
--
https://www.freebsd.org/doc/handbook/filesystems-linux.html

create memory disk (md) and format it to msdos or other file system
--

how to check file system i am using?
--
/dev/ufs/rootfs on / (ufs, local, journaled soft-updates) # so i am using UFS

freebsd support format sys utility
--
which newfs

@venus-> ls /sbin/| grep newfs
newfs
newfs_msdos

mount
--
which mount
ls /sbin | grep mount

partition table
--
sade (sade is menu driven like gpart, man sade)

dd if=/dev/zero of=./30M.img bs=1M count=30
mdconfig -a -f ./30M.img 
sade