IntroductionThis 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. DetailsText marked with [] shows user input. Determine which device the SD Card Reader is on your systemPlug 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 CardNote 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 fdiskBe sure to choose the whole device (/dev/sdc), not a single partition (/dev/sdc1). $ [sudo fdisk /dev/sdc] Print the partition recordSo 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 alreadyCommand (m for help): [d]
Selected partition 1 Set the Geometry of the SD CardIf the print out above does not show 255 heads, 63 sectors/track, then do the following expert mode steps to redo the SD Card: Command (m for help): [x] - Set the number of heads to 255.
Expert Command (m for help): [h]
Number of heads (1-256, default xxx): [255] - Set the number of sectors to 63.
Expert Command (m for help): [s]
Number of sectors (1-63, default xxx): [63] - Now Calculate the number of Cylinders for your SD Card.
#cylinders = FLOOR (the number of Bytes on the SD Card (from above) / 255 / 63 / 512 )
So for this example: 2021654528 / 255 / 63 / 512 = 245.79. So we use 245 (i.e. truncate, don't round). - Set the number of cylinders to the number calculated.
Expert Command (m for help): [c]
Number of cylinders (1-256, default xxx): [enter the number you calculated] Expert Command (m for help): [r] Print the partition record to check your workCommand (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 Create the FAT32 partition for booting and transferring files from WindowsCommand (m for help): [n]
Command action
e extended
p primary partition (1-4)
[p]
Partition number (1-4): [1]
First cylinder (1-245, default 1): [(press Enter)]
Using default value 1
Last cylinder or +size or +sizeM or +sizeK (1-245, default 245): [+50]
Command (m for help): [t]
Selected partition 1
Hex code (type L to list codes): [c]
Changed system type of partition 1 to c (W95 FAT32 (LBA)) Mark it as bootableCommand (m for help): [a]
Partition number (1-4): [1] Create the Linux partition for the root file systemCommand (m for help): [n]
Command action
e extended
p primary partition (1-4)
[p]
Partition number (1-4): [2]
First cylinder (52-245, default 52): [(press Enter)]
Using default value 52
Last cylinder or +size or +sizeM or +sizeK (52-245, default 245): [(press Enter)]
Using default value 245 Print to Check Your WorkCommand (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 51 409626 c W95 FAT32 (LBA)
/dev/sdc2 52 245 1558305 83 Linux Save the new partition records on the SD CardThis is an important step. All the work up to now has been temporary. Command (m for help): [w]
The partition table has been altered!
Calling ioctl() to re-read partition table.
WARNING: Re-reading the partition table failed with error 16: Device or resource busy.
The kernel still uses the old table.
The new table will be used at the next reboot.
WARNING: If you have created or modified any DOS 6.x
partitions, please see the fdisk manual page for additional
information.
Syncing disks. Format the partitionsThe two partitions are given the volume names LABEL1 and LABEL2 by these commands. You can substitute your own volume labels. $ [sudo mkfs.msdos -F 32 /dev/sdc1 -n LABEL1]
mkfs.msdos 2.11 (12 Mar 2005)
$ [sudo mkfs.ext3 -L LABEL2 /dev/sdc2]
mke2fs 1.40-WIP (14-Nov-2006)
Filesystem label=
OS type: Linux
Block size=4096 (log=2)
Fragment size=4096 (log=2)
195072 inodes, 389576 blocks
19478 blocks (5.00%) reserved for the super user
First data block=0
Maximum filesystem blocks=402653184
12 block groups
32768 blocks per group, 32768 fragments per group
16256 inodes per group
Superblock backups stored on blocks:
32768, 98304, 163840, 229376, 294912
Writing inode tables: done
Creating journal (8192 blocks): done
Writing superblocks and filesystem accounting information: Bootloader settingsIf you use bootloader U-Boot, use following settings to mount root file system at second partition from kernel: console=ttyS2,115200n8 root=/dev/mmcblk0p2 rw rootdelay=1
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Typical usage with uImage in 1st partition and rootfs in 2nd partition:
setenv bootargs 'console=ttyS2,115200n8 root=/dev/mmcblk0p2 rw rootdelay=1' setenv bootcmd 'mmcinit;fatload mmc 0 80300000 uImage;bootm 80300000'
When I used the FAT32 partition and it worked fine for me.
when I followed the above procedure, sometimes I can have two partitions when I plug the SD card again. sometime only the first partition appears, what about the problem?
Be careful not to type 't' '1' 'c' - if you follow the above to the letter, you don't need to specify the partition number to change the type for. You know you have done it wrong if the partition type for partition 1 is now set to 'FAT12'. The spurious 'c' will then toggle some compatibility flags that may affect your system.
As noted elsewhere, there is a typo under "Create the FAT32 partition for booting and transferring files from Windows". Type simply 51? and not the +50 as indicated. Also, for unknown reasons, after the first fdisk on a SanDisk? 2GB SD Card (about the most common card you can find) the total bytes shows up under fdisk as 1977614336 and not the full 2GB. When you do the calculation above, you end up with number of cylinders = 240, not 245. My resulting SD Card was not recognized by the X-Loader until I corrected this.
When I try to boot with the usual bootargs and bootcmd environment, the kernel is booted and root is mounted. But then I get the message: "Unable to open an initial console" and it hangs.
BTW, is the serial port ttyS0 or ttyS2? I can see the boot messages only with ttyS2.
Robert
Robert, were you able to solve the issue with "Unable to open an initial console"? I'm still stuck as that stage.
ID
As noted by challinan, enter 51 in the Create the FAT32 partition for booting and transferring files from Windows section.
Hi When do we have to enter command : console=ttyS2,115200n8 root=/dev/mmcblk0p2 rw rootdelay=1 ??? When Flash is mounted on PC, after changing labels ? This is not clear for me Thaks PL
"Unable to open an init console"....
I got this from another forum. You need to untar the root file system to the second partition. Therefore after you copy the necessary files in Windows to the first partition (angstrom.whatever_this_is.tar.bz2) then you need to untar the files. In knoppix I did the following:
$ sudo mount -t msdos /dev/sda1 /media/sda1/ $ sudo mount -t ext3 /dev/sda2 /media/sda2/ $ cd /dev/sda1/ $ sudo tar xvjf ./Angstrom.whatever_this_is.tar.bz2 -C /dev/sda2/
This will take some time. Then unmount the drives and remove the SD card.
Sorry, that last line should read "-C /media/sda2"