I am performing a backup using the following command with a su shell:

dd if=/dev/block/mmcblk0 of=/mnt/expand/ee131623-1634-25d1-9f9f-902b68eceaee/mmcblk0.img"

And I was wondering if this would fail to complete as it would include the backup in the backup?

Is Internally formatted external sd cards included in mmcblk0?

  • from my understanding this should work and there is no way to include something at block layer
    – alecxs
    Commented Nov 5, 2019 at 23:51

1 Answer 1


No. Internally formatted external sd card is not included in mmcblk0. dd dumps files, in your case the block device file mmcblk0 which includes all partitions, GUID partition table (GPT) and any free space in between partitions.

External SD card is a separate flash memory chip, so exposed by a different block device available at path something like /dev/block/mmcblk1 or /dev/block/sda.

  • except for some very old devices (Samsung/Nexus?) they have separate so called "sdcard" partition on mmcblk0 (and additional external MicroSd Card mmcblk1)
    – alecxs
    Commented Nov 7, 2019 at 14:42
  • Right. Actually mmcblk1 is a convention for external SD card and sda for USB OTG etc. Yes a separate partition mmcblk0p* was used for external storage before /data/media was started being emulated. Commented Nov 7, 2019 at 14:55

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