Overview

The mmccopy utility is an easier-to-use alternative to dd for writing images to SDCards and MMC memory. It has the following features:

1. Write image data from stdin or a file directly to an offset on the device (this is similar to dd except that offsets are specified in bytes instead of blocks)

2. Batch up writes into 1 MiB blocks by default to improve transfer rate. (dd defaults to 512 byte blocks without the bs argument)

3. Automatically unmount partitions that are using the device. This prevents data corruption either due to latent writes from the mounted file systems or due to image writes being cached.

4. Provide human and machine readable progress similar to using pv with dd, except with the improvement that the percentages track completed writes rather than initiated writes.

5. Automatic detection of MMC and SDCards. This option queries the user before writing anything by default to avoid accidental overwrites.

6. Optionally run a TRIM command on the MMC or SDCard before writing to it. This lets you quickly reset the entire memory contents even if you're only going to write a fraction of it. This is only available on devices and SDCard readers that support the TRIM command.

Here's an example run:

$ sudo mmccopy -p sdcard.img
Use memory card found at /dev/sdc? [y/N] y
100%
$

Building from source

Clone or download the source code and run the following:

./autogen.sh
./configure
make
make install

Invoking

Usage: mmccopy [options] [path]
  -d <Device file for the memory card>
  -n   Report numeric progress
  -o <Offset from the beginning of the memory card>
  -p   Report progress (default)
  -q   Quiet
  -r   Read from the memory card
  -s <Amount to read/write>
  -t   Run the TRIM command on the memory card before copying
  -v   Print out the version and exit
  -w   Write to the memory card (default)
  -y   Accept automatically found memory card

The [path] specifies the location of the image to copy to or from
the memory card. If it is unspecified or '-', the image will either
be read from stdin (-w) or written to stdout (-r).

Examples:

Write the file sdcard.img to an automatically detected SD Card:
  mmccopy sdcard.img

Read the master boot record (512 bytes @ offset 0) from /dev/sdc:
  mmccopy -r -s 512 -o 0 -d /dev/sdc mbr.img

Offset and size may be specified with the following suffixes:
    b  512
   kB  1000
    K  1024
  KiB  1024
   MB  1000000
    M  1048576
  MiB  1048576
   GB  1000000000
    G  1073741824
  GiB  1073741824