Introduction

This page tells you how to turn an ordinary SDHC card into a Balsa jaunty SD card for the OLPC. It uses a Windows Computer. The steps are:

• download the information (image file) for the Balsa SD card
• check the image file
• extract the image (IMG) file
• copy it to an SD card.

If you have already built a Balsa beta-1 card, the process is the same, except for the file you download, and the checksum file that you check it against.

If you already have the programs to extract the image (IMG) file and copy it to an SD card, you can use the same programs and instructions.

The downloads for this are about 700 megabytes of data.

This process writes over the SD card completely. Any existing data on the card will be lost.

Downloading the Image

Download the Balsa jaunty SD card image, either the 4 gigabyte version or the 8 gigabyte version, depending on the size of the SD card. This will create a large file of type .7z on your computer.

Remember the folder that you've downloaded it to. You will need it later. Your browser/downloader probably has an "Open containing folder" option if you right-click on the download in the downloader window. You can use that to remember.

 Download for 4 gig SD (698 Mbytes)

Download for 8 gig SD (695 Mbytes)

Checking the Image Using an MD5sum

After you've downloaded the Balsa image, you need to use an MD5sum to check to see that the file has downloaded correctly. An explanation of this MD5sum check is available after these instructions:

Instructions for Checking the Image

1. Download this zip file that contains the MD5sums(.exe) program.
2. Right-click on the zip file and choose Extract All. There will be a check box that says Show extracted files when complete. Make sure it is checked.
3. Windows Explorer will open with a folder containing the md5sums(.exe) program.
4. Open another Windows Explorer window to the folder that contains your copy of the image. That's the folder you remembered when you downloaded the image.
5. Drag the Balsa image file icon (it will be a .7z file) from one window onto the md5sums program icon in the other window. The md5sums program will calculate the MD5 number for your Balsa image file and display it in a window.
6. Click on one of these link for the 4 gigabyte version MD5 or the 8 gigabyte version MD5, depending on which image file you downloaded.
7. If the MD5sums are the same (you only have to check the first few letters), the download was good. If you aren't going to download another large image, you can delete the md5sums program and proceed to Extracting the Image Using 7-Zip.
8. If the MD5sums are different, there was a problem with the download, and you should download the image again.

How the MD5sum Check Works

The MD5sum is used to check to see if there's an error in a large download. There's a number called an MD5sum that can be calculated for any file. The MD5sum is unique to that file, and a small change in the file will make a completely different MD5sum.

You download a small program that calculates the MD5sum of a file, and use it to calculate the MD5sum for your copy of the Balsa image. If your MD5sum is the same as the one we've calculated, you know your copy of Balsa image is the same as ours. If the two MD5sums aren't the same, you know that the download had an error. Because even a small error makes a completely different MD5sum, you don't have to check more than the first few letters and numbers.

Extracting the Image Using 7-Zip

The Balsa image was compressed using a program called 7-Zip. Here is how to extract the Balsa image file using 7-Zip.

1. Download the 7-Zip program from 7-zip.org.  You will probably want the version for Windows-32.
2. Install it in Windows.
3. Run the 7-Zip file manager and extract the .img file contained in the Balsa image (.7z file)that you downloaded.

You will now have an extracted Balsa image (IMG) file, either just under 4 gigabytes or just under 8 gigabytes on your computer. Once you have the extracted image file you can make multiple Balsa SD cards with it. The file is very large so, if you need the space on your computer, you can just keep the compressed Balsa image and use 7-Zip to extract it when you want to make a new Balsa SD card.

Copying the Image to the SD Card

When you have an extracted Balsa image (IMG) file, the next step is to copy the image to the SD card. This is done by the Win32DiskImager program.

1. Plug in the SD card and take note of its drive letter.  If a window opened for the card, close it.
2. Download this zip file that contains the Win32DiskImager program.
3. Right-click on the zip file and choose Extract All. Make sure the check box that says Show extracted files when complete is checked.
4. Windows Explorer will open with a folder containing the Win32DiskImager program.
5. Double-click on the program to run it. The program allows you to select an IMG file and a device to copy to.
6. Select the extracted Balsa image (IMG) file that 7-Zip made.
7. Select the SD card using its drive letter as the device.
8. Click on the Write button.
9. The Win32DiskImager program will warn you that you may corrupt the drive. This is because it will overwrite everything on the SD card.
10. Let the program proceed.

When the Win32DiskImager program is finished, the SD card will be a Balsa Jaunty SD card for the OLPC XO.

You can use the card to set up a machine to run Balsa, either the machine you just used to produce the card or a different machine.