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[edit] SD Configuration and Setup

There are 2 approaches to format the SD card. You could either use the script available or follow the step by step instructions below.

Note: All these instructions are common across all OMAP platforms.

[edit] Script to partition/format SDCards

Want to avoid all of the below mentioned instructions and use a simple script instead? See the below link (the script is a bit dangerous!):

The script has now been moved into the Ångström contrib area in OE See below link:

You can also use this script which will refuse to use /dev/sda as the device (that tends to be your primary HDD!).

if [ ! "$1" = "/dev/sda" ] ; then
	if [ -b "$DRIVE" ] ; then
		dd if=/dev/zero of=$DRIVE bs=1024 count=1024
		SIZE=`fdisk -l $DRIVE | grep Disk | awk '{print $5}'`
		echo DISK SIZE - $SIZE bytes
		CYLINDERS=`echo $SIZE/255/63/512 | bc`
		echo ,9,0x0C,*
		echo ,,,-
		} | sfdisk -D -H 255 -S 63 -C $CYLINDERS $DRIVE
		mkfs.vfat -F 32 -n "boot" ${DRIVE}1
		mke2fs -j -L "rootfs" ${DRIVE}2

After running the script mount the SD card partitions on host:

mkdir /tmp/mmc1<br>
mkdir /tmp/mmc2<br>
sudo mount /dev/sdx1 /tmp/mmc1<br>
sudo mount /dev/sdx2 /tmp/mmc2<br><br>

Verified to work on Ubuntu to boot boards such as beagle, omapzoom2 etc. A big thanks to XorA!

[edit] Step by Step Instructions to format SD card

Since putting a Linux file system on a FAT32 partition is problematic, it is recommended to also create a 2nd partition.

The card shows up as /dev/sd*. To identify the card, you can either do:

For this example

sudo fdisk /dev/sdc
Command (m for help): p
Disk /dev/sdc: 1018 MB, 993001472 bytes

Look for the size in bytes of the device and calculate the number of cylinders, dropping fractions, if we have 255 heads and 63 sectors (and 512 bytes per sector so 1 cylinder is 255 * 63 * 512 = 8225280 bytes).

new_cylinders = Size / 8225280 (for this example we will have 993001472 / 8225280 which equals 120.725 or 120 cylinders)

[edit] Delete existing Partitions

Since we are changing the underlying geometry of the disk, we must clear the partition table before doing it. So delete all partitions using the fdisk 'd' command - yes, you will lose all data on the card. Once that is done, we can set the new geometry in expert mode. We will set the number of heads to 255, number of sectors to 63, and number of cylinders to new_cylinders.

Command (m for help):  d
Partition number (1-4): 1
Command (m for help):  d
Partition number (1-4): 2

[edit] Configure SD Card

Command (m for help): x
Expert command (m for help): h
Number of heads (1-256, default 30): 255
Expert command (m for help): s
Number of sectors (1-63, default 29): 63
Warning: setting sector offset for DOS compatiblity
Expert command (m for help): c
Number of cylinders (1-1048576, default 2286): <new_cylinders calculated from above> 

[edit] Configure SD Partitions

Now we return to the main menu and create 2 partitions as needed - 1 boot partition of 64Meg and the rest a linux partition.

Expert command (m for help): r
Command (m for help): n
Command action
e extended
p primary partition (1-4)
Partition number (1-4): 1
First cylinder (1-123, default 1):
Using default value 1
Last cylinder or +size or +sizeM or +sizeK (1-123, default 123): +64M (see note above)
Command (m for help): n
Command action
e extended
p primary partition (1-4)
Partition number (1-4): 2
First cylinder (10-123, default 10):
Using default value 10
Last cylinder or +size or +sizeM or +sizeK (10-123, default 123):
Using default value 123

[edit] Fat32 Partition

Command (m for help): t
Partition number (1-4): 1
Hex code (type L to list codes): c
Changed system type of partition 1 to c (W95 FAT32 (LBA))
* You have to format 1st partitions with vfat32 filesystem.
Command (m for help): a
Partition number (1-4): 1

[edit] Check Partition Table

The partition table should look something like the following. Notice the heads, sectors, and cylinders. Make sure partition 1 is active and FAT32. If it looks good - write the new partition information out.

Command (m for help): p
Disk /dev/sdc: 993 MB, 993001472 bytes
255 heads, 63 sectors/track, 120 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Disk identifier: 0x00000000

Device Boot Start End Blocks Id System
/dev/sdc1 * 1 9 72261 c W95 FAT32 (LBA)
/dev/sdc2 10 120 891607+ 83 Linux

Command (m for help): w
The partition table has been altered!

Calling ioctl() to re-read partition table.

WARNING: If you have created or modified any DOS 6.x
partitions, please see the fdisk manual page for additional
Syncing disks.

[edit] Formatting Partitions

Format the filesystems on the partitions:

# sudo mkfs.vfat -F 32 -n boot /dev/sdc1
# sudo mkfs.ext3 -L filesystem /dev/sdc2

[edit] Creating a mount point

mkdir /tmp/mmc1
mkdir /tmp/mmc2
sudo mount /dev/sdc1 /tmp/mmc1
sudo mount /dev/sdc2 /tmp/mmc2

[edit] Problem seen with FDISK not erasing the first sector

The fdisk utility does not seem to erase the first few bytes of the first sector in the card when the partition table is saved.

Use dd to erase the first sector.

dd if=/dev/zero of=/dev/<sdb> bs=1024 count=1

Then use the procedure listed in section above to create new partitions and format them accordingly

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