I'm new to reverse engineering.

I only want to add an app to my sat receiver.

To start I tried to extract my firmware with ./extract-firmware, it's ok, and I have 1 ecos RTOS, and two cramfs in fmk/

BUT when I rebuild without any change, I have a message

Building new cramfs file system... (this may take several minutes!)
Directory data: 464 bytes
Everything: 1392 kilobytes
Super block: 76 bytes
CRC: b79c2a52
Remaining free bytes in firmware image: 856064
Processing 0 header(s) from /home/thehou/firmware-mod-kit/fmk/new-firmware.bin...
CRC update failed.

Firmware header not supported; firmware checksums may be incorrect.
New firmware image has been saved to: /home/thehou/firmware-mod-kit/fmk/new-firmware.bin`

So before I continue to add an app into my sat receiver, I want to know how can I rebuild my extracted firmware.

Perhaps must I extract with binwalk, but I don't know how to rebuild!

Thanks for your help.

Reference : this is the receiver firmware

  • Some firmwares have one or more text files containing hashes for files or filesystem images. Perhaps one of them no longer matches; maybe you used slightly different compression or something. See if a file like that exists, and update any hashes that may have changed. – multithr3at3d Apr 2 at 0:19
  • Based on "firmware checksums may be incorrect.". There also could be a custom header with hashes instead. – multithr3at3d Apr 2 at 0:26

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