[finnix] Replace ddrescue with gddrescue?

[Sylvan Heuser]

On Thu, 2010-04-15 at 10:00 +1000, Michael D. Setzer II wrote:
> Does someone has a clear difference between ddrescue and gddrescue?
I think the Linux Journal article (see below) is enough to get an idea,
but you can always read the manpages:
apt://gddrescue, ddrescue: http://manpages.debian.net/cgi-bin/man.cgi?query=ddrescue
apt://ddrescue, dd_rescue: http://manpages.debian.net/cgi-bin/man.cgi?query=dd_rescue

To put it simple: apt://gddrescue is the "advanced" clone of
apt://ddrescue. As far as I understand, someone adopted the old
apt://ddrescue code, added functionality - and it ended up in the GNU
project.

Also recommended:
http://www.debianadmin.com/recover-data-from-a-dead-hard-drive-using-ddrescue.html#comment-839
(The article is about dd_rescue, but the comment sums up some nice
benefits of ddrescue)

> Note the ddrescue wasn't that big, but it require the libstdc++ 
> library, which wasn't part of my image. Perhaps finnix already has that 
> library.
Right... dependencies. mh. That could indeed be a problem, although
Ryan's intentions were to keep Finnix below 185MiB, not below 100MiB,
weren't they? Haven't checked yet if there is already some 

> I replaced the older dd_resuce with the ddrescue, and am looking at allowing 
> using more than the basice ddrescue source destination options.
basic options? What basic options? They're all just copying files... and
have the option to control harddisks directly to some extent.

> Does the gddrescue have additional option that would be helpful in disk / 
> partition backups?
Look at the comment to the debianadmin article - I won't paste
everything in here.

> As a final thing, can the complied gddrescue be ftped to a running finnix 
> boot, and then run? In the past I had a method to download an run g4l from 
> a finnix cd.
I wouldn't know why to use ftp, but you can certainly use precompiled
packages under finnix - that's how I currently use apt://gddrescue,
although I thought about creating my own custom "overlay".

> > > when you say "more advanced" what do you mean?
> > 
> > http://www.linuxjournal.com/magazine/hack-and-when-disaster-strikes-hard-drive-crashes?page=0,1 
> > > ddrescue or dd_rescue 
> > > To make things a little confusing, there are two similar tools with
> > > almost identical names. dd_rescue (with an underscore) is an older
> > > rescue tool that still does the job, but it works in a fairly basic
> > > manner. It starts at the beginning of the drive, and when it
> > > encounters errors, it retries a number of times and then moves to the
> > > next block. Eventually (usually after a few days), it reaches the end
> > > of the drive. Often bad blocks are clustered together, and in the case
> > > when all of the bad blocks are near the beginning of the drive, you
> > > could waste a lot of time trying to read them instead of recovering
> > > all of the good blocks.
> > > 
> > > The ddrescue tool (no underscore) is part of the GNU Project and takes
> > > the basic algorithm of dd_rescue further. ddrescue tries to recover
> > > all of the good data from the device first and then divides and
> > > conquers the remaining bad blocks until it has tried to recover the
> > > entire drive. Another added feature of ddrescue is that it optionally
> > > can maintain a log file of what it already has recovered, so you can
> > > stop the program and then resume later right where you left off. This
> > > is useful when you believe ddrescue has recovered the bulk of the good
> > > data. You can stop the program and make a copy of the mostly complete
> > > image, so you can attempt to repair it, and then start ddrescue again
> > > to complete the image.
> > 
> > Especially the logfile feature is sometimes crucial, for example when
> > you need to copy an image in two parts because of limited space on your
> > transfer medium.

-- 
S.