建立200mb的ramdisk，md1解除 md4

# mdconfig -a -t swap -s 200m -u 1
# newfs -U md1
/dev/md1: 200.0MB (409600 sectors) block size 16384, fragment size 2048
        using 4 cylinder groups of 50.02MB, 3201 blks, 6464 inodes.
        with soft updates
super-block backups (for fsck -b #) at:
 160, 102592, 205024, 307456
# mount /dev/md1 /mnt
# df /mnt

解除 md4

# mdconfig -d -u 4

參考資料

[1] http://www.freebsd.org/doc/en_US.ISO8859-1/books/handbook/disks-virtual.html