75XX MicroSD Recovery

If backing up on a separate workstation, keep in mind windows does not have direct block device support needed to write these images. You will also need to determine the SD card device. You can usually find this in the output of 'dmesg' after inserting the SD card and you will typically see something like '/dev/sdb' as the block device and '/dev/sdb1' for the first partition. On some newer kernels you will see '/dev/mmcblk0' as the block device and '/dev/mmcblkop1' for the first partition. For these examples I will use the '/dev/mmcblk0' format.

If you are backing up directly on the board you will likely need to use some kind of offboard storage like a thumbdrive or external hard drive. Make sure you have any nbd devices unmounted before trying to restore new ones.

You can find the latest SD card image here. Make sure you decompress the image first before writing.

From Workstation

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Backup

Entire SD card

dd if=/dev/mmcblk0 of=/path/to/backup.dd bs=32k

Kernel

dd if=/dev/mmcblk0p2 of=/path/to/zImage bs=32k

Initrd

dd if=/dev/mmcblk0p3 of=/path/to/initrd bs=32k

Restore

Entire SD card

dd if=/path/to/backup.dd of=/dev/mmcblk0 bs=32k

Kernel

dd if=/path/to/zImage bs=32k of=/dev/mmcblk0p2

Initrd

dd if=/initrd bs=32k of=/dev/mmcblk0p3

From SBC

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Backup

Entire card

# Determine the block size
eval $(sdctl)
dd if=/dev/nbd5 of=/path/to/backup.dd bs=512 count=$cardsize_sectors conv=sync

Kernel

sdctl -R 4096 -z 512 --seek part1 > kernel

Initrd

sdctl -R 4096 -z 512 --seek part2 > initrd

Restore

The entire card from SBC

dd if=/path/to/2gbsd-noeclipse-latest.dd bs=512 conv=sync of=/dev/nbd5

Kernel

dd if=/mnt/root/zImage bs=512 conv=sync of=/dev/nbd7

Initrd

dd if=/mnt/root/initrd bs=512 conv=sync of=/dev/nbd8

Expected Partition Layout

Partition	Contents
1	FAT32 (empty)
2	kernel binary (0xda)
3	initrd (0xda)
4	Debian root filesystem (EXT3)