32

Long story short, I'm working on a Windows 7 machine and I'd like to strip the image off an SD card (backing up the card from a Raspberry Pi). I'm trying to use Cygwin, but not having much success.

Examining the /dev directory, it looks like my SD card is showing up as sdd and sdd1. However, when I run the following command:

dd if=/dev/sdd of=RPi.img

I get the following:

dd: opening '/dev/sdd': Permission denied

I've used dd on a Mac and under Linux without any problem, using similar syntax. What am I missing with Cygwin?

Peter Mortensen
  • 12,326
GrandAdmiral
  • 475

6 Answers6

33

You get the Permission denied error, because you are not root. That sounds strange in the context of Cygwin, but it hits home.

When you query your status (id) in a normally started Cygwin shell, you'll get something like that:

$ id
uid=1001(user) gid=545(Users) groups=545(Users),555(Remote Desktop Users),513(None)
$ dd if=/dev/sda bs=1000 count=1 | wc -c
dd: opening `/dev/sda': Permission denied
0

Under Windows 7 the trick to become root in Cygwin is to start the session elevated, that is, do a right click on your Cygwin icon and choose Run as Administrator. Now your are still not root itself, but at least in root's group:

$ id
uid=1001(user) gid=545(Users) groups=545(Users),0(root),544(Administrators),555(Remote Desktop Users),513(None)

And now, dd works as you are used to it from Un*x:

$ dd if=/dev/sda bs=1000 count=1 | wc -c
1+0 records in
1+0 records out
1000 bytes (1.0 kB) copied, 0.00104424 s, 958 kB/s
1000
mpy
  • 28,816
15

I recently had to clone one USB drive to another on windows. My drive is a multiboot with additional software so I didn't want to just copy all files on the FS. DD was a clear choice, but I wasn't on linux so there were a few things I had to do to get it working.

I had cygwin installed and did the following.

first I had to figure out what /dev/sdX device my f: volume was. To do so run this command in cygwin. (TIP: Make sure you start cygwin with admin privs.. *Right click on cygwin and "Run as Administrator")

    cat /proc/partitions
which should output:
   8 0 3813383838 sda
   8 1       4031 sda3 C:\
   8 15  30588303 sdb 
   8 15  30588303 sdb1 E:\
   8 21  30530020 sdc
   8 22  30530020 sdc1 F:\

etc... Here you can clearly see for me to clone my F: drive to my E: drive I'd issue the following command.

There is one more step actually, you have to find the root of your device. Look for an sd* that has a size of your device. This whould be easy as the size should be well known such as 8GB, 16GB, 32GB expanded as bytes as shown above. 

dd if=/dev/sdc of=/dev/sdb bs=8M

My image was 32gb.. and I didn't want to just sit and wait with a blinking cursor.. I wanted to see progress so I installed "pv" in cygwin. 

dd if=/dev/sdc | pv | dd of=/dev/sdb bs=8M

Now if you want to copy the thumbdrive to an image do the following.

dd if=/dev/sdX | pv | dd of=/cygdrive/c/Users/Myname/Desktop/mythumbdrive.img bs=8M

Hope this helps

CaesarS
  • 125
Jaime
  • 251
3

I've had success with dd for Windows, which I believe is a rewrite rather than a port. It's open-source and does not rely on Cygwin.

I particularly liked the dd --list command, which listed all the disk devices along with enough info to identify the one I wanted.

RomanSt
  • 9,959
2

Will something like USB Image Tool do?
Or, do you insist on using Cygwin? ...

nik
  • 57,042
1

HDD Raw Copy Tool can make copies of an SD card. If you select "Raw image (dd image)" in the save dialog then it will be identical to the ones made with dd. You can restore images too.

I know it's not done via cygwin, but I personally wouldn't trust it with accessing raw devices.

Hayley
  • 220
0

I see that RaspberryPi.org is now recommending Win32 Disk Imager for writing images to SD Memory Cards. It will also read images from the card, so I'm trying it out now.

GrandAdmiral
  • 475