How to create a dual-partition card for BeagleBoard to boot Linux from first partition and have root file system at second partition.

Introduction

This guide is meant for those looking to create a dual-partition card, booting from a FAT partition that can be read by the OMAP3 ROM bootloader and Linux/Windows, then utilizing an ext3 partition for the Linux root file system.

Details

Text marked with [] shows user input.

Determine which device the SD Card Reader is on your system

Plug the SD Card into the SD Card Reader and then plug the SD Card Reader into your system. After doing that, do the following to determine which device it is on your system.

$ [dmesg | tail]
...
[ 6854.215650] sd 7:0:0:0: [sdc] Mode Sense: 0b 00 00 08
[ 6854.215653] sd 7:0:0:0: [sdc] Assuming drive cache: write through
[ 6854.215659]  sdc: sdc1
[ 6854.218079] sd 7:0:0:0: [sdc] Attached SCSI removable disk
[ 6854.218135] sd 7:0:0:0: Attached scsi generic sg2 type 0
...

In this case, it shows up as /dev/sdc (note sdc inside the square brackets above).

Check to see if the automounter has mounted the SD Card

Note there may be more than one partition (only one shown in the example below).

$ [df -h]
Filesystem            Size  Used Avail Use% Mounted on
...
/dev/sdc1             400M   94M  307M  24% /media/disk
...

Note the "Mounted on" field in the above and use that name in the umount commands below.

If so, unmount it

$ [umount /media/disk]

Start fdisk

Be sure to choose the whole device (/dev/sdc), not a single partition (/dev/sdc1).

$ [sudo fdisk /dev/sdc]

Print the partition record

So you know your starting point. Make sure to write down the number of bytes on the card (in this example, 2021654528).

Command (m for help): [p]

Disk /dev/sdc: 2021 MB, 2021654528 bytes
255 heads, 63 sectors/track, 245 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

   Device Boot      Start         End      Blocks   Id  System
/dev/sdc1   *           1         246     1974240+   c  W95 FAT32 (LBA)
Partition 1 has different physical/logical endings:
     phys=(244, 254, 63) logical=(245, 200, 19)

Delete any partitions that are there already

Command (m for help): [d]
Selected partition 1

Set the Geometry of the SD Card

If the print out above does not show 255 heads, 63 sectors/track, then do the following expert mode steps to redo the SD Card:

• Go into expert mode.

Command (m for help): [x]

• Set the number of heads to 255.

Expert Command (m for help): [