Flashing or backing up your SD card¶

How to do it under MacOs and Linux. For both these tasks you will need the dd program. It comes with many Linux distributions and is available for MacOS.

Backing up your SD card¶

Put your SD card in the SD card reader. We assume for the rest of this document that your SD card is /dev/mmcblk0

Start by unmounting the SD card in case it is currently mounted:

$ sudo umount /dev/mmcblk0

In case your partition is smaller than the size of the sd card, you do not need to backup the whole card, so if this is the case, run:

$ sudo fdisk -u -l /dev/mmcblk0

You might get something along the lines of

            Device Boot      Start         End      Blocks   Id  System
    /dev/mmcblk0p1   *          63      144584       72261    c  W95 FAT32 (LBA)
    /dev/mmcblk0p2          144585     3743144     1799280   83  Linux

You are interested in the higher value in the "End" column. Pass that value to dd as the count parameter:

$ sudo dd conv=sparse count=3743144 if=/dev/mmcblk0 of=bbb_images/your_own_your_precious_backup_image.img