How can I change a single file from an UBI image

Question

I have an ubi image file (.ubi) and I want to change a single file from that image (/etc/network/interfaces to be precise).

How can I change a single file from that ubi image?

I'm using OS X but I have a Ubuntu VM as well.

It seems no difference between ubifs images and images of other fs: unpack image or mount-loop exists image, make some changes and rebuild finally image. I found this link and hope this will be helpful for you - slatedroid.com/topic/3394-extract-and-rebuild-a-ubi-image. — Yurij Goncharuk, Mar 5 '18 at 12:33
@YurijGoncharuk Thank you. I already had a look at this link and got stuck because mtdblockmodprobe and ubimodprobe wasn't found by modprobe. — d3L, Mar 5 '18 at 12:54

d3L · Accepted Answer · 2018-03-06 13:34:37Z

Ok after a lot of reading, I finally figured it out how to do it on Ubuntu:

1.) Simulate a NAND MT-device with nandsim

modprobe nandsim first_id_byte=... second_id_byte=.. third_id_byte=.. fourth_id_byte=...

2.) Find out the MT-device id

cat /proc/mtd | grep -i "NAND Simulator"

3.) Load UBI kernel module

modprobe ubi

4.) Erase MT-device (you may skip this step)

flash_erase /dev/mtdX 0 0

5.) Flash the UBI image with ubiformat

ubiformat /dev/mtdX -y -f /path/to/ubi -O XXXX -s XXXX

6.) Attach MT-device to UBI with ubiattach and note the UBI device number

ubiattach -p /dev/mtdX

7.) Mount it with mount

mount -t ubifs ubiX /path/to/mount-point/

8.) Make the changes.

9.) Create UBIFS with mkfs.ubifs

mkfs.ubifs -o ubifs.img -m XXXX -e XXXX -c XXXX -v -r /path/to/mount-point/

10.) Create UBI image with ubinize

ubinize -o final.ubi -p XXXX -m XXXX -s XXXX -v ubinize.cfg

XXXX = Parameter that is specific to the NAND flash chip used.

ubinize.cfg looks something like this:

[rootfs]
mode=ubi
image=ubifs.img
vol_name=rootfs
vol_flags=autoresize
vol_type=dynamic
vol_id=0

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