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Create Image From SD Card: How To Create a Bit-By-Bit File Clone

We will look at how to create images from SD cards below. Like hard drives and SSDs, SD cards are storage devices that you can use to create bootable drives. But when you store critical information in them, it is essential to have a backup to help you recreate the original data in case of data loss. You can copy the files as they are, but creating image files from this SD card data is better. Let’s look at how to form these image files by first defining a disk image.

What Is a Disk Image?

A disk image is a compressed file of a bit-by-bit, sector-by-sector copy of a computer hard drive’s contents or other storage media. In this context, it is a compressed file containing a copy of the contents in your SD card. This bit-by-bit file copying is ideal for backups because it creates an identical, bit-by-bit clone that you can restore later.
Create Image From SD Card: An SD card being inserted into a computer

An SD card being inserted into a computer

How To Create an Image File From SD Card in Windows

In Windows, you can use the Win32 Disk Imager or DD-for-Windows utility tool. You will also need a PC with a card reader or an SD card-to-USB adapter to connect to your PC.

Using Win32 Disk Imager

Begin by connecting the SD card you want to clone to your computer using its built-in card reader or a Micro SD card-to-USB adapter. Download the Win32 Disk Imager tool, then install and run the application. Click the drop-down arrow under “Device” in the pop-up window to pick the drive letter. Check under “My Computer” to see which letter your SD card has taken. After that, click the folder icon immediately left of the letter you selected. Pick a location in your computer for storing the image file, and give it a name. This file should have a .img extension. Click the “Read” button to begin the cloning process. Give your PC some time and don’t shut it off, close the lid, or put it to sleep. When the process is complete, a window will appear to show successful reading. You can now delete the contents in your SD card and use it to store other things.

Image File Restoration Using Win32 Disk Imager

Insert the SD card into your computer and open the Win32 Disk Imager tool. Select the drive letter in the device drop-down section, then click the folder icon to access the file from where you saved it. Instead of clicking “read,” click “write” and give your PC time to complete the restoration process. The tool will save the image in your memory card, making it appear as when you created the backup file. Generally, the image creation and restoration process length depends on the SD card size. It is vital to note that the image creation or backup matches the SD card size, not the contents stored in the card. For instance, if the SD card capacity is 32GB, the image file will be 32GB even if the data inside only occupies 1 GB. Remember, a disk image is a bit-by-bit copy. So it clones the data and sectors in the storage media.
Create Image From SD Card: A 32GB SD card

A 32GB SD card

So creating a disk image for a 32GB SD card and restoring it takes more time than doing the same for an 8GB card, even if the amount of data inside is the same. And the former will occupy more space in your hard drive.

DD for Windows

Windows operating systems lack the DD command line utility. But it is ubiquitous in Linux and Unix systems. However, you can download DD for Windows externally. After downloading, unzip the file and note its file location. Next, connect the SD card to your PC and note its disk number. It should be disk one if you don’t have other removable storage devices plugged into your computer. After that, open the command line and run it as an administrator. You can hit the windows button, then type “cmd.” Right-click the command line result from the search and select run as administrator. In the cmd window, change the directory using the cd command to the directory where you extracted the DD utility tool. Next, enter type this line, then hit enter to clone the SD card contents into an image file.
The DD command takes three parameters to do the cloning.
  • IF: input file, which is the SD card (we assume the disk number is 1)
  • OF: output file, which states the storage location and file name of the image
  • BS: block size, which is one megabyte
Give your PC some time to complete the image creation process.

Image File Restoration Using DD

Before restoring the image file, use the diskpart tool to clean the SD card and its formatting. But be careful not to clean data in other disks. Go to the computer management tool to ensure you have the correct disk number, then use these commands in the cmd panel. In this case, the disk number is 1.
After that, use this DD command to copy the image to the card.
This line switches the position of the input file and output file parameters because we are reversing the image creation process. And remember to run the cmd tool as an administrator.

How To Create an Image File From SD Card in Linux

The DD utility tool is present natively in Linux systems, so you don’t need to install anything. Connect the SD card to your computer and open a terminal window. Enter this command to list all file systems connected to the system.
Locate your SD card name from the results using its size. For instance, a 16GB SD card will have a listed capacity of 14.9 GB. Note the correct device name. It should be something like “/dev/sdb.” Use this DD command to create a clone image file on your PC.
This command format resembles the Windows DD tool format, except it has a sudo command and lacks the block size parameter. Sudo enables you to run commands with root privileges (equivalent to “run as administrator” in Windows). Hit enter and give your PC some time to complete cloning.

Image File Restoration Using DD in Linux

Before restoring the image, unmount the SD card partitions using this command.
In this case, the SD card name is “sdb.” Replace this parameter if your storage device has a different name. Hit enter. If the result is blank, the micro card has no disk partitions, and you can proceed to restoration. But if you see multiple card partitions like sdb1, sdb2, and sdb3, run this terminal command to unmount them.
After that, use this DD command to restore the image file.
Hit enter and wait for a confirmation message from DD of process completion.

How To Create an Image File From an SD Card in MacOS

After connecting the SD card to your computer, use the “diskutil list” in the terminal window to find your SD card’s device ID. It will be slightly different from what you get in Linux systems. For instance, it can be “/dev/disk4.” Next, unmount the micro card using this command.
Create the card backup in your computer’s hard drive using this command.
Wait to get a process completion message from DD in the terminal window.

Image File Restoration Using DD in MacOS

First, unmount the destination card using this terminal command.
Next, use this DD command to restore the card image file.
Wait for the DD confirmation message after completion.

Wrap Up

As you can see, creating a backup image file requires only a few commands. But be careful when selecting the drive letter or disk number. And we recommend using an SD card size that matches the capacity of the content stored inside to avoid memory wastage. For instance, if you want to backup 3GB of data, use a 4GB card. That’s it for this article. Let us know if it was insightful in the comments below.