Converting raw Nikon NEF files to DNG and back on Linux

Regardless of whether it makes sense or not to convert raw files to DNG, you might choose a middleground solution and embed the original raw file in a DNG file.
The major drawback to this solution is that the resulting DNG file will be roughly double in size when compared with the original raw file.
The benefit of emdedding a raw files in a DNG file that you can easily extract it later on.

Step 1 - Install Adobe DNG Converter

You can find a very good tutorial on how to install it on Linux on RawTherapee’s website: https://rawpedia.rawtherapee.com/How_to_convert_raw_formats_to_DNG#Installing_Adobe_DNG_Converter_in_Linux

Once DNG Converter is installed, create a dng alias to start it from CLI:

alias dng='WINEPREFIX="$HOME/WinePrefixes/DNGConverter" wine "$HOME/WinePrefixes/DNGConverter/drive_c/Program Files/Adobe/Adobe DNG Converter/Adobe DNG Converter.exe"'

Step 2 - Convert NEF files to DNG

cd to a directory with your NEF files and simply execute:

dng ./

It will bring the DNG Converter window up:

Click Change Preferences and check Embed Origianal Raw File:

Lastly, hit Convert button and wait for the conversion to finish: 03-dng_converter_conversion_status.png

Step 3 - Extract embeded RAW NEF file from DNG

To extract an emdedded RAW NEF file from a DNG file, we’ll use the amazing ExifTool by Phil Harvey.

exiftool -b -originalrawimage DSC_0001-original.dng > DSC_0001-extracted.nef

Step 4 - Compare extracted file with the original

To ensure that both files are identicall, run a simple diff:

$ diff --report-identical-files DSC_0001-original.nef DSC_0001-extracted.nef
Files DSC_0001-original.nef and DSC_0001-extracted.nef are identical