[bug-ddrescue] Ddrescue warns if mapfile exists

[Antonio Diaz Diaz]

Hi Shahrukh,

Shahrukh Merchant wrote:
> Seems like there should be a warning (with a flag to override the
> warning) and some action by ddrescue to recognize the use of an old
> mapfile. E.g., include the source and/or destination disk ID in the
> mapfile (perhaps in a special comment field for backward compatibility)
> and warn if either or both are different.

This can be a can of worms. To begin with, obtaining the device ID is not 
portable. Even device size is not always available. See for example the 
description of '--verify-input-size' in the manual:
http://www.gnu.org/software/ddrescue/manual/ddrescue_manual.html#Invoking-ddrescue

-I
--verify-input-size
Compare the size of infile with the size calculated from the list of blocks 
contained in the mapfile, and exit with status 1 if they differ. This is not 
enabled by default because the size of some devices can't be known in 
advance and because the size derived from the mapfile may be incomplete, for 
example after doing a partial rescue.

Moreover, ddrescue already warns when the mapfile exists. See 
http://www.gnu.org/software/ddrescue/manual/ddrescue_manual.html#Output

     GNU ddrescue 1.24
     Press Ctrl-C to interrupt
     Initial status (read from mapfile)
     rescued: 1665 MB, tried: 0 B, bad-sector: 0 B, bad areas: 0


Best regards,
Antonio.