Gumstix Developer Center

Create a Bootable MicroSD Card

1. Hardware setup
2. Get an image
3. Create a bootable microSD card
4. Boot your Gumstix system

With the image that you got in the last step, you are ready to create a microSD card with which to boot your Gumstix system.

Supported microSD Cards

Gumstix DuoVero COMs and Overo COMs support SD cards that comply with the SD Association's SD I/O Card Specification version 2.0, including SDHC cards.

Prepare Your microSD Card

1. On your development machine, insert your microSD card into the card reader. 

2. Determine the device filename of your microSD card in the form sdX, where X is a letter assigned by your computer, using the following command:

   $ dmesg

   The device name will be in the fourth column between square brackets. E.g.,

   [ 23468.560268]	sd 8:0:0:0: [sdb] 3862528 512-byte logical blocks: (1.97/1.84 GiB)
   [ 23468.562125]	sd 8:0:0:0: [sdb] No Caching mode page present
   [ 23468.562128]	sd 8:0:0:0: [sdb] Assuming drive cache: write through
   [ 23468.564871]	sd 8:0:0:0: [sdb] No Caching mode page present
   [ 23468.564874]	sd 8:0:0:0: [sdb] Assuming drive cache: write through
   [ 23468.564874]	sdb: sdb1 sdb2 sdb3

   In this example, our microSD card has a device filename of sdb, and is 2 GB (1.97 GB) in size. When using the device filename in commands, always remember to use its full path, i.e., /dev/sdb. Note any output showing the filename with a numbered suffix (e.g., sdb1, sdb2 and sdb3 above) as you will need it in the next step.

   To automatically insert your device name in the following steps, enter the device filename as it appeared in the previous command's output, but without square brackets:

   Device name: 

   This will automatically add your device's full path for the rest of this stage in the Getting Started Guide.

3. Mounted partitions on the drive have numbers after the device name and are shown on the last line of the dmesg output above. Unmount any mounted partitions on the attached device:

    $ sudo umount /dev/<DEVICE NAME>{1,2,3}

   where 1, 2, 3, are the numbers shown after the device name in the last line of your dmesg output. You can use as many as you need separated by commas.

   Partitions vs. Drives: In Linux, a physical block device such as a hard drive or an SD card appears in the /dev directory (e.g., /dev/sdb). This device file refers to the entire physical device.

   A single physical device can contain multiple individual partitions each with their own file system. These partitions also appear in the /dev directory under the same name, but include a suffix for the partition number (e.g., /dev/sdb1, which is partition #1 of the physical device sdb). Linux makes the file systems on these partitions available by mounting them to a directory in the existing file system. Removable devices are typically mounted to mount points in the /mnt or /media directories.

   In the above example, the physical device /dev/sdb has one partition, /dev/sdb1 which is mounted to the mount point /media/Portable.

4. Users of Yocto Project or Angstrom images only: Click here for some additional steps.

   Additional Steps for Yocto Project or Angstrom Users

   Yocto Project or Angstrom users need to partition and format their microSD cards manually in order to flash an image.

   1. Your microSD card needs a special geometry to make the best use of its memory and to be accessible by the DuoVero or Overo boot ROM.

      Calculate the required number of cylinders for your particular card with the following steps:

      1. Find the size of your card in the output of the following command:

         $ sudo fdisk -l /dev/<DEVICE NAME>
         Disk /dev/<DEVICE NAME>: 2016 MB, 2016411648 bytes

         The card size is the bolded number above, and may vary depending on what size of card you use.

      2. Divide the card size in bytes by 255 heads, 63 sectors and 512 bytes per sector and round down to the nearest integer.

         Enter the size in bytes from the last step below:

         E.g., ÷ 255 ÷ 63 ÷ 512 → 245

         This is the number of cylinders needed for your drive's geometry.

   2. To use these images, your microSD card has to have two partitions: a FAT partition containing the boot files and a Linux partition containing the root file system. To create these partitions:

      1. Clean up any existing partition data:

         $ sudo dd if=/dev/zero of=/dev/<DEVICE NAME> bs=1024 count=1024

      2. Create the new partitions using sfdisk:

         $ sudo sfdisk -D -uM -H 255 -S 63 -C <NUMBER OF CYLINDERS FROM STEP 1.2> /dev/<DEVICE NAME>

         At the sfdisk prompt, type 0,64,0x0C,* followed by Enter to set up a 64 MB bootable FAT32 partition.

         At the following prompt, type 75,,,- followed by Enter to create the root filesystem partition.

         For the next two prompts, type 0,0,, followed by Enter. Make sure you do this twice.

         When prompted, type y + Enter to write the partition table.

      3. Finally, you must format the partitions. First, create the boot partition. Be sure to specify the number of the partition to format after /dev/<DEVICE NAME> (e.g., /dev/sdb1, /dev/sdb2):

         $ sudo mkfs.vfat -F 32 /dev/<DEVICE NAME>1 -n boot

         If your computer is missing the mkfs.vfat program, try installing the dosfsutils package and try again:

         $ sudo apt-get install dosfsutils

         Now create the Linux root filesystem partition:

         $ sudo mke2fs -j -L rootfs /dev/<DEVICE NAME>2
         

   Your microSD card is now ready to be flashed with the boot and root filesystem images.

Write the Images to microSD

Select the line of Gumstix COM you are using:

1. Hardware setup
2. Get an image
3. Create a bootable microSD card
4. Boot your Gumstix system