Newbie needs mmc device help

I am confused on mmc device names.

When I boot my Beaglebone Black with (or without) an unformatted micro SD card it looks like the system recognizes only the FLASH on mmcblk0, like I would expect:

beaglebone:/media# sfdisk -l

Disk /dev/mmcblk0: 58624 cylinders, 4 heads, 16 sectors/track
sfdisk: Warning: The partition table looks like it was made
for C/H/S=*/255/63 (instead of 58624/4/16).
For this listing I’ll assume that geometry.

Units = cylinders of 8225280 bytes, blocks of 1024 bytes, counting from 0

Device Boot Start End #cyls #blocks Id System
/dev/mmcblk0p1 * 0+ 8 9- 72261 c W95 FAT32 (LBA)
/dev/mmcblk0p2 9 232 224 1799280 83 Linux
/dev/mmcblk0p3 0 - 0 0 0 Empty
/dev/mmcblk0p4 0 - 0 0 0 Empty

Disk /dev/mmcblk0boot1: 32 cylinders, 4 heads, 16 sectors/track

But when I find documentation on formatting the Micro SD card (see below), it refers to formatting mmcblk0 which scares me because I don’t want to destroy the on-board FLASH…

So my questions are:

  1. Wouldn’t referring to mmcblk0 target/destroy the on board FLASH?
  2. How do I refer to a non-formatted device (how are these named)?
  3. Am I correct in assuming that any device connected to the eMMC ports of the CPU will be assigned an “mmcblk” device name?

For instance (

export DISK=/dev/mmcblk0
sudo dd if=/dev/zero of=${DISK} bs=1M count=16
sudo sfdisk --in-order --Linux --unit M ${DISK} <<-EOF

"DISK=/dev/mmcbkl0" is just an assumption.. Run "lsblk" and select the
proper disk name..