[Bug-ddrescue] Reply to bugs in the manual, concerning the --fill-mode chapter

[Анонимный отправитель]

Hello, Prashant Subbarao and Antonio Diaz Diaz!
I have news for the latest bug reports. My message is at the bottom of this 
letter.
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Sent: Sunday, July 17, 2016 7:00 PM
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1. possible bug on GNU ddrescue (Prashant Subbarao)
> Message: 1
> Date: Sat, 16 Jul 2016 17:17:35 -0400
> From: Prashant Subbarao <address@hidden>
> To: address@hidden
> Subject: [Bug-ddrescue] possible bug on GNU ddrescue
> Message-ID:
> <address@hidden>
> Content-Type: text/plain; charset=UTF-8
> 
> Dear Mr. Antonio Diaz Diaz or To Whom It May Concern:
>  Following the instructions on the man page (
> https://www.gnu.org/software/ddrescue/manual/ddrescue_manual.html#Fill-mode),
> I am attempting to use GNU ddrescue to fill the bad sectors in my recovered
> hard disk with a random string, "RMEUHEJB", that I have put into a tmpfile.
> address@hidden:~/Desktop$ printf "RMEUHEJB" > tmpfile
> address@hidden:~/Desktop$ sudo ddrescue --fill-mode=l- tmpfile /dev/sdc 
> rescue.JustPlusMinus.log
> *ddrescue: unrecognized option `--fill-mode=l-'*
> *Try `ddrescue --help' for more information.*
> I get the error above (emphasis added for clarity). I copied and pasted the
> command straight from the man page, only changing the target device and
> mapfile; so I don't think I made a mistake in the execution of the command.
> Can you please advise me? I really appreciate your help and prompt
> attention to this.
> Best Regards,
> Prashant Subbarao

I may help in this case. Reading carefully the manual, we find the correct 
usage examples for --fill-mode:
The fill mode has a number of uses. See the following examples:
Example 1: Mark parts of the rescued copy to allow finding them when examined 
in an hex editor.
For example, the following command line fills all blocks marked as '-' 
(bad-sector) with copies of the string 'BAD SECTOR ':
     printf "BAD SECTOR " > tmpfile
     ddrescue --fill-mode=- tmpfile outfile mapfile
Example 2: Wipe only the good sectors, leaving the bad sectors alone.
This way, the drive will still test bad (i.e., with unreadable sectors).
This is the fastest way of wiping a failing drive, and is specially useful when 
sending the drive back to the manufacturer for warranty replacement.
     ddrescue --fill-mode=+ --force /dev/zero bad_drive mapfile
Example 3: Force the drive to remap the bad sectors, making it usable again. If 
the drive has only a few bad sectors, and they are not caused by drive age, you 
can probably just rewrite those sectors, and the drive will reallocate them 
automatically to new "spare" sectors that it keeps for just this purpose. 
WARNING! This may not work on your drive.      
     ddrescue --fill-mode=- -f --synchronous /dev/zero bad_drive mapfile

So, for your purpose, Prashant, you should use the following command lines:
printf "RMEUHEJB" > tmpfile
sudo ddrescue --fill-mode=- tmpfile /dev/sdc rescue.JustPlusMinus.log

Antonio, there is really a BUG in the following one line of the online manual, 
there should be "-" (minus) instead of "l-" (L minus):
https://www.gnu.org/software/ddrescue/manual/ddrescue_manual.html#Fill-mode - 
Example 4
ddrescue --fill-mode=l- tmpfile cdimage mapfile
should be:
ddrescue --fill-mode=- tmpfile cdimage mapfile

One more issue - I can not understand the option "-dr9" in the following line 
of the online manual:
   ddrescue -b2048 -i0x12345000 -s2048 -dr9 /dev/cdrom cdimage mapfile
Is it meaningful, or is it just another misprint/mistake in the manual?