Problem copying SD card with `dd` on OSX

Question

i am trying to back up my sd-card(16GB) with Mac using:
sudo dd if=/dev/rdisk3 of=~/Desktop/raspberrypi20161117_r.dmg bs=1m

Output:
dd: /dev/rdisk3: Input/output error 2996+0 records in 2996+0 records out 3141533696 bytes transferred in 170.479861 secs (18427594 bytes/sec)

The Input/output error always comes when 3141533696 bytes transferred.

dd output with /dev/disk3

Outupt:
dd: /dev/disk3: Device not configured 2996+0 records in 2996+0 records out 3141533696 bytes transferred in 1507.614168 secs (2083778 bytes/sec)

The sd-card still works with raspberry pi...

I hope someone can help me to backup the sd card

Thanks

Answer 1

One option would be to try ApplePi Baker from Tweaking4All

I've found it has handled cards where DD failed but TBH it does look like the card has a real issue and Rsync may be the only way get your data off.

I would not try to rescue the OS unless you have a very specific config - if you have lost an OS file the new card could die at the wrong moment in the future and you end up with duff data or failing application.

Remember the old advice - backup frequently and often.

Answer 2

You could try ddrescue or fsck on the Pi (this should run by default if the OS detects an error, but can be manually run).

However I would recommend you get a new SD card, mount it on the Pi in a card reader and use the SD Copy utility in Raspbian to copy to the new card. This actually does a file copy (using rsync) so should recover all the readable files. You may lose a file or so, but it is quite likely the card error is on a part of the file which is unused.

Answer 3

First, you have to make sure you are using the right device for your input. Open a terminal window, then:

$> lsblk Locate your SD card device. You will have e.g. :

[...]
sdf      8:80   1   7,5G  0 disk 
├─sdf1   8:81   1   256M  0 part /media/m/boot
└─sdf2   8:82   1   7,3G  0 part /media/m/rootfs

sdf is my device for input, not sdf1 or sdf2.

$> sudo dd bs=4M status=progress conv=fsync if=/dev/sdf of=/{full_path}/backup_SD.img

to get your full_path use $> pwd

Your errors come from, maybe partition notation (/dev/rdisk3) instead of device (can't check on MacOS), and of=~, the ~ is not interpreted here.

If you still got errors, give some outputs.