Can't back up SD card with dd, complains "I / O error",

Question

I have successfully backed up my SD card twice by issuing the following command

sudo dd if=/dev/sdb of=/home/user/Documents/raspi/images/raspi1.v2.iso bs=1M 

However, now it gives me the following error:

 dd: reading `/dev/sdb': Input/output error 3027+1 records in 3027+1 records out 3174977536 bytes (3.2 GB) copied, 200.723 s, 15.8 MB/s 

Looking back at the network, this seems to indicate a damaged SD card. However, my raspi (which I escaped from this SD card) is working fine (ish) and Disk Utility claims that the SD card is not damaged.

Is there any other way to find out why dd complains if the card is damaged, and if so, how to fix the SD card.

UPDATE:

I gave up trying to run dd on the SD card, but I realized that it was distorting my SD card, this is a Raspi firmware update, as indicated on this site

Answer 1

It is possible that your raspi just didn’t hit the badblock on the SD card, and therefore it works fine.

You can dd the image and ignore bad blocks by adding the conv=noerror . This will replace the bad blocks with zeros, and if you return this image back to another card of the same size, it should work the same.