Goal

UPDATE: fixed a bug with the number of cylinders. Now cards larger than 2gb will register their full size.

A script that can be run by a someone not familiar with the instrinsics of the Gumstix Overo to create a boot-image-ready microSDHC card of any size.

In the case that the script runs on the overo:

sudo partition-overo-sdhc.sh /dev/mmcblk0

In the case that the script runs on another Linux box:

sudo partition-overo-sdhc.sh /dev/sdf

Script

The following script automates the process described by Gumstix Overo: Creating a bootable microSD card

It may be run on the Gumstix Overo or on a system with an appropriate microSDHC reader.

/usr/local/bin/partition-overo-sdhc.sh:

#!/bin/bash
#http://www.gumstix.net/Setup-and-Programming/view/Overo-Setup-and-Programming/Creating-a-bootable-microSD-card/111.html

# set this script to exit at any point an operation returns failure
set -e

# Create the environment for this script
DEV=$1
DEFAULT_DEV=/dev/mmcblk0
IS_OVERO=`cat /proc/cpuinfo | grep Overo || true`
IS_MMCBLK=`echo ${DEV} | grep /dev/mmcblk || true`

if [ ! -n "${DEV}" ]
then
  if [ -n "${IS_OVERO}" ]
  then
    echo "About to partition (DESTROY data) ${DEFAULT_DEV}"
    DEV=${DEFAULT_DEV}
    echo "CTRL+C now if that's not what you wanted..."
    sleep 3
    echo "continuing..."
  else
    echo -n 'Usage: `'$0' /dev/MICRO_SDHC_BLOCK_DEVICE`'
    exit 1;
  fi
fi

# Attempt to ensure that the disk is not in use
umount ${DEV} 2>/dev/null || true
umount ${DEV} 2>/dev/null || true

# Backup the MBR - in case the working hard drive is specified by mistake, rather than the sd card
dd if=$DEV of=./mbr.bak bs=512 count=1 2> /dev/null
echo "Created backup of MBR... just to be safe"
echo 'use `dd of='${DEV}' if=./mbr.bak bs=512 count=1` to restore or `rm mbr.bak` to remove'

# Calculate what the number of cylinders should be according to the overo uboot specs
let BYTES=`fdisk $DEV -l | grep Disk | grep bytes | cut -d',' -f2 | cut -d' ' -f2`
CYL=$(($BYTES/255/63/512))

# This scripts fdisk to run in expert mode
# it changes the head, sector, and cylinder, to match those required for the overo uboot
# it then creates a 32mb FAT boot partition and uses the rest of the card for the rootfs
#
# Comments may not be placed between the EOF blocks below
fdisk $DEV << EOF >/dev/null 2>/dev/null || true
o
x
h
255
s
63
c
$CYL
r
n
p
1
1
+32M
t
c
a
1
n
p
2
6

w
EOF
# The return of this process is almost always false due to that the kernel cannot resync the
# partition table.
# A reboot (on the overo) or unplugging and replugging the sdhc (on a Linux box)
# is required before continuing on to copy over the SD image.

# Overo Note:
# if the `reboot` command doesn't work use
# echo b > /proc/sysrq-trigger
# which is similar to a hard power cycle

echo -n "Probably prepared SD card successfully..."
if [ -n "${IS_OVERO}" ] && [ -n "${IS_MMCBLK}"  ]
then
  echo "The overo should be rebooted (to resync the partition table with the kernel) because you can't hot-swap/reinsert the microSDHC."
  echo 'Try `reboot` (soft, but sometimes hangs) or `cd /; umount -a; sync; echo b > /proc/sysrq-trigger` (power cycle)'
else
  echo "The microSDHC must be removed from and reinserted into the card reader to continue"
fi

Updated at 2010-08-19

[Home] Partition MicroSDHC for Gumstix Overo

Goal

Script