Mount DD image on Linux
Yesterday, my Raspberry Pi running Arch Linux was not able to boot with error:
Kernel Panic, not syncing: no init found. I spent a night on it, but could not find a working solution. The last option is easy: reinstall the system. That is really the last resort, for I do not want to re-setup everything I have done: samba server, Time Machine server, Xunlei Offline Downloader…
Unable to mount the SD card
The system does not boot, so I need to find a way to get into the file system to identify what is wrong, or at least backup all the configuration files.
I cannot directly mount it on my Mac, due to the unsupported Ext4 format, although the boot partition can be mounted, as it is in FAT format. I did tried with ext4fuse and fuse-ext2 without luck. I could neither connect the inter SD card reader to Parallel Desktop VM running Ubuntu, what a pity!
Use DD to make the SD card to an image
This is really a workaround, but it indeed is the best solution I am having.
* Locate the SD card by running
diskutil list. It is disk2
* Make image file using dd:
sudo dd if=/dev/disk2 of=~/Desktop/pi.img bs=1m
Mount the image in Ubuntu
I did this in my Parallel Desktop running Ubuntu.
fdisk to list partition information of the image.
fdisk -u -l pi.img
the result I got was:
Disk pi.img: 15.9 GB, 15931539456 bytes 255 heads, 63 sectors/track, 1936 cylinders, total 31116288 sectors Units = sectors of 1 * 512 = 512 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disk identifier: 0x0004f23a Device Boot Start End Blocks Id System pi.img1 * 2048 186367 92160 c W95 FAT32 (LBA) pi.img2 186368 31116287 15464960 83 Linux
We will be using this command to mount the image:
mount -o loop, offset=[offset value] [path to image file] [path to mount point]
Take note of the unit size, 512 byte here and the Start sector for each partition, which are used to calculate the offset. Here I want to mount the second partition, pi.img2. With a simple calculation: 512 * 186368 = 95420416
sudo mount -o loop,offset=95420416 pi.img /media/pi
Ok, that’s it. Now I am able to explore the files.