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• Question ids are NOT guaranteed to remain fixed, and may change between releases; the questions also do differ between products.
  It is therefore strongly recommended that you (re)generate a  preseed file for each release.
• Some questions can be asked repeatedly with different dynamic arguments, but it is only possibly to  preseed one answer for all these invocations.
  For example, question 6868, "Ok to OVERWRITE changed file $item\nor No to abort installation?" may be asked multiple times for different values of '$item'. The preseed file can only provide one answer which is then used for all of them.
• Preseeded answers can at this time not contain the double quote character.
• The paths given for -P  and -p  must be absolute ones, ie. /some/directory/filename.

Method of finding questions which are mistakenly not carrying a preseed value

grep -rRnP 'input_yn\s+?"[^"]*?"\s*?;' bin