1) The output of the dmesg command after you've issued one of these dd commands 
and waited
a few seconds?

If freshly formatted, it presents itself, mounted with the following
dmesg:

[45841.715089] mmc0: card 0002 removed
[45847.861632] mmc0: new SDHC card at address 0003
[45847.862012] mmcblk0: mmc0:0003 SD16G 14.8 GiB 
[45847.863443]  mmcblk0: p1

I too was surprised to see it mounted as mccblk0 device and not a
/dev/sd*.

- sudo dd if=./mmcblk0p1.bin of=/dev/mmcblk0p1 bs=10M 
- Sometimes, after about 400 KB no more data is written to the device.
- Then dd seems to be uninterruptable unless I issue kill -9 

It stays like this until I end the process with ejecting the card or
killing dd.

2) Information on the make/model/capacity of the SD card you are using.

Its a 16Gb Kingston class 6 SDHC inserted directly into the card reader of the 
T420.
- Reading from the card, formatting and writing files to it works approximatley 
10-20Mbps.
- Formatting it FAT32 works ok and has been used in canon cameras.
- Using it as a truecrypt partition also works fine, reading and writing is 
quite respectable.
- Reading using dd works at around 10Mbps.


Oddly enough, while writing up these notes, I formatted the SDHC with gparted.  
And now, instead of hanging around 400KB written it continues to copy almost 
all of the 14.8GiB.  But right at the end has failed with an error message - 
insufficient disk space.  Which is odd, because the image was taken from an 
exact same SDHC card make and model.  It seems it failed very close to the end 
of the device memory at 14.8GiB.

sudo dd if=./mmcblk0.bin of=/dev/mmcblk0 bs=1024
dd: writing `/dev/mmcblk0': No space left on device

If I wish to clone an entire SDHC card, should I dd the device or just
the partition?  That is: mmcblk0 or mmcblk0p1?  Is it necessary to
format the SDHC first?  I would not think so, but thought I'd ask.

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https://bugs.launchpad.net/bugs/975305

Title:
  dd writing to an SDHC /dev/mmcblk0

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