I need to be able to access the two eMMC "boot" partitions on an SD Card from my Ubuntu 14.04 system with USB-SD Card adapter. The SD card is actually an embedded eMMC device plugged-in to an SD Card adapter board, but it looks just like an SD Card.

The kernel documentation says the boot partitions are accessible as /dev/mmcblkXboot0 and /dev/mmcblkXboot1. When I plug in the SD card to my system, it mounts as /dev/sdc and I can see the "user" partition on the card, but not the boot partitions, which I know exist because I can seem them in another system.

The boot partitions do not contain any mountable filesystem, but they contain raw data used by firmware on another system. I just want to be able use dd to read/write the boot partitions.

I'm pretty sure I did this a couple years ago using a laptop with a built-in SD card reader and running a different version of Linux (not sure if it was Ubuntu).

Can anyone help with how to do this on Ubuntu 14.04?

lsblk output:

bwelch@bwelch-linux:~$ lsblk
sda       8:0    0 149.1G  0 disk 
├─sda1    8:1    0 141.1G  0 part /
├─sda2    8:2    0     1K  0 part 
└─sda5    8:5    0   7.9G  0 part [SWAP]
sdc       8:32   1 229.3M  0 disk 
├─sdc1    8:33   1   128K  0 part 
├─sdc2    8:34   1     9M  0 part 
├─sdc3    8:35   1    72M  0 part /media/bwelch/disk3
├─sdc4    8:36   1     5M  0 part 
├─sdc5    8:37   1    19M  0 part /media/bwelch/disk1
├─sdc6    8:38   1   128K  0 part 
├─sdc7    8:39   1   128K  0 part 
├─sdc8    8:40   1   128K  0 part 
├─sdc9    8:41   1     9M  0 part 
├─sdc10   8:42   1    72M  0 part /media/bwelch/disk2
├─sdc11   8:43   1     5M  0 part 
├─sdc12   8:44   1    19M  0 part /media/bwelch/disk
├─sdc13   8:45   1   128K  0 part 
├─sdc14   8:46   1   128K  0 part 
├─sdc15   8:47   1   7.5M  0 part /media/bwelch/697838c1-c1d3-49f0-adf4-ad22d143291a
└─sdc16 259:0    1   7.5M  0 part /media/bwelch/ef831e0f-002f-4d68-8b28-1a81eb86f68e
sr0      11:0    1  1024M  0 rom  
  • What's the output of lsblk? – You'reAGitForNotUsingGit Mar 27 '17 at 18:33
  • Instead of posting it in a comment, please edit your question to include the output in a code block. – You'reAGitForNotUsingGit Mar 28 '17 at 21:08
  • sdc1-16 are logical GPT partitions within the eMMC's user partition and they are correct, but the boot0 and boot1 partitions do not show. I'm thinking this may be a property of the USB card reader (and probably all USB card readers). I looked for a native PCIe card reader, but they are difficult to find. There are lots of mini-PCIe-to-SD adapter cards, but they seem to all use the USB signals in the mini-PCIe slot instead of native PCIe. – Brian Welch Mar 28 '17 at 21:08
  • @AndroidDev OK figured out the code block method. Sorry, not used to this style of question/answer formatting rules. – Brian Welch Mar 28 '17 at 21:16

I got confirmation that this behavior is, in fact, a property of the card reader. The USB card reader exposes only a USB mass storage device, so the software doesn't even know there's an SD/eMMC card. The card reader would have to expose the boot partitions as separate devices, but it doesn't, which is normal.

I need to find way to attach a native SD/eMMC interface to my host PC. When I did this a couple years ago, I used an older laptop with an integrated SD card reader and I presume it had a native SD interface. The only add-in native readers I can find now use the now-discontinued Ricoh R5U230 chipset, but I'm not sure if Linux drivers are available for it.

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