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Re: dd question, what am I doing wrong?



On Sat, 2009-12-05 at 11:02 -0800, Daniel B. Thurman wrote:
> Patrick O'Callaghan wrote:
> > On Fri, 2009-12-04 at 16:13 -0800, Daniel B. Thurman wrote:
> >   
> >> The problem I have specifically with rsync (or tar, or cp) is that
> >> it does not save ACLs, file attributes too well, and so on that I
> >> gave up using it.  Perhaps the problem in this case is not to use
> >> the -a option but to use the manual options to save everything
> >> about the files that you can.
> >>
> >> Specifically:
> >> rsync manual:
> >> -a, --archive        archive mode; equals -rlptgoD (no -H,-A,-X)
> >> -H, --hard-links   preserve hard links
> >> -A, --acls             preserve ACLs (implies -p)
> >> -X, --xattrs          preserve extended attributes
> >>     
> >
> > Do you mean that you've tried these (particularly -A and -X) and they
> > don't work? If so, have you filed a bug report?
> >   
> I am not certain that it's a bug per-se, it's just that there are
> cases, or so it seems, where it is not clear how to deal with
> the issue on my part.  For example, hard links (-H).  How are
> hard links handled on one drive to be copied over to another
> and is it guaranteed to work?  I could not get my mind around
> this one so I did not want to take a chance.

Well, you could try it. Since you're copying to a fresh drive anyway,
there's no harm in doing it and checking the result.

Hard links are an easy case in fact, and trivial to check. Create file A
and hard link B to it. Rsync A and B to a different filesystem, using
the -H option. Use "ls -i" on the copied files to see that they both
have the same inode. That's all a hard link is.

> As for ACLs (-A),
> what exactly is being handled here and does this work for ALL
> Oses concerned - do they follow the same "standard"?

WTF? Of course not. I thought we were talking about Linux here. In fact
there's been no indication in this thread of anything to the contrary.
There is no "standard" for this stuff across OSes (I suppose Posix might
be considered a standard but I'd be very careful about relying on it).
We're doing low-level system maintenance here. Don't expect anything to
be portable.

> I am thinking
> about Vista in particular, so I did not want to experiment on this
> one either.

I wouldn't dream of doing this on a non-Unix system.

> As for extended attributes (-X), I have no clue exactly
> what this is.  I guess I have to someday take the time to do more
> research before messing around with these rsync options.  This is a
> particular reason why I am using dd/rescue & resizing - it works sans
> Vista, which I have yet to try.

Again, rsync is a *Unix* utility, designed for *Unix* filesystems
*only*. If you'd said at the beginning that you wanted to move a Vista
partition we could have saved ourselves a lot of time.

poc


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