Boot from SD card: where is DISK=/dev/sdX?

I am following this guide to create an bootable SD card:

I am stuck at mkfs.ext4 <= 1.42:
for``: DISK=/dev/mmcblk0 <<--- Do I include this ‘for:’ in the command or no? The terminal on my Ubuntu is complaining that no ‘for’ command can be found.
for: DISK=/dev/sdX``` <<— `Where is this sdX drive? lsblk does not show any of that name.

Please help. Thank you so much.

Replace the "X" with what would be valid for your drive..


It's a script meant to be interpreted by the human, not the computer.
You didn't blindly copy and paste the "As the version of U-Boot needed
for this target CAN NOT correctly handle reading files with these newer
ext4 options." did you?

To translate:

- If you set DISK=/dev/mmcblk0 (or similar); use the command:
  sudo mkfs.ext4 -L rootfs -O ^metadata_csum,^64bit ${DISK}p1

- Otherwise, if you set DISK=/dev/sdX (where X is one or more
  arbitrary letters); then use this command instead:
  sudo mkfs.ext4 -L rootfs -O ^metadata_csum,^64bit ${DISK}1

Thinking about this, the following would be the copy-and-paste shell
equivalent (note; I have not tested this):

case "${DISK}" in
        sudo mkfs.ext4 -L rootfs -O ^metadata_csum,^64bit ${DISK}p1
        sudo mkfs.ext4 -L rootfs -O ^metadata_csum,^64bit ${DISK}1

That might be worth putting on the wiki… not sure who has access.

Thank you, everyone. That was helpful.