'adb backup -apk -shared -all -f "D:\backup.ab' initiates backup, completes, but produces a file that is only 1kb I'm attempting to backup my old Android device, a Samsung Galaxy S3, so that I can lend it to my friend while his is away at repairs, then restore it when he's done with it.

I have the Samsung USB drivers installed, and the device is recognised. 

C:\Users\...\AppData\Local\Android\sdk\platform-tools&gt;adb devices
List of devices attached
4df7f9574edecf7f        device


I set a developer password, as per this post, which caused the "Backup starting..." to last about 3 seconds longer than before. It completes successfully, then produces a file that is 1kb. 

C:\Users\...\AppData\Local\Android\sdk\platform-tools&gt;adb backup -all -f D:\backup.ab
Now unlock your device and confirm the backup operation.

C:\Users\...\AppData\Local\Android\sdk\platform-tools&gt;




Does anybody know what's going on?

Thanks in advance.
Try with more parameters, like:

adb backup -all -apk -obb -shared -nosystem -f "yourFile.ab"

*Unless you have a rooted phone I don't recommend -system, use -nosystem instead.