rsync - Oct 2005 - [Bug 3175] devices and --link-dest don't seem to work together

https://bugzilla.samba.org/show_bug.cgi?id=3175





------- Additional Comments From foner-rsync-bugzilla@media.mit.edu  2005-10-17
04:36 -------
Created an attachment (id=1518)
 --> (https://bugzilla.samba.org/attachment.cgi?id=1518&action=view)
Transcript of unsuccessful attempts

I have other transcripts with me experimenting with all four possibilities of
trailing or no trailing slash on the link-dest & source directories, just in
case that was confusing things; I couldn't find a combination that worked. 
(And it can't -all- be pilot error, anyway, since dirvish was having the
same
problems, and only on the device files.)


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https://bugzilla.samba.org/show_bug.cgi?id=3175


wayned@samba.org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |ASSIGNED




------- Additional Comments From wayned@samba.org  2005-10-17 12:24 -------
Only regular files are currently hard-linked together via --link-dest.  I have
been hesitant to add to add hard-linking of non-regular files because it will
not always be supported and it doesn't save much space, but perhaps it
wouldn't
be too complex to code this up.

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https://bugzilla.samba.org/show_bug.cgi?id=3175





------- Additional Comments From wayned@samba.org  2005-10-17 12:27 -------
Created an attachment (id=1519)
 --> (https://bugzilla.samba.org/attachment.cgi?id=1519&action=view)
Allow --link-dest to affects symlinks and devices

I've worked up a patch for testing that appears to handle things pretty
well.
It still needs some improvement, though -- i.e. I need to add some code that
would discern if a failed hard-link attempt means that a symlink or device
cannot be hard-linked, or if just this attempt failed.

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------- Additional Comments From foner-rsync-bugzilla@media.mit.edu  2005-10-17
15:27 -------
Oh!  I had no idea --list-dest -wasn't- supposed to work with devices (and
symlinks), given that the documentation for the option said nothing about the
restriction and given that rsync does handle devices (and symlinks) correctly in
other contexts.  So I'd say that was a documentation bug... :)

In any event, I've applied your patch (thanks! how speedy! :) and rerun my
quick
test---works fine.  (Also passes all the tests in make test, except for two it
rightly skipped [chmod-temp-dir and ssh-basic].)  I'm now rerunning my
full-up
dirvish to make sure that works as well; I should know the results in 90 minutes
or so (and will comment again if it doesn't work).

If you're concerned about this not working in all cases (or on all
filesystems---makes it hard to just check at configure time) and maybe tossing
spurious errors if it -doesn't- work, I guess there's always the
possibility of
Yet Another Rsync Option to tell it not to try.  I have no particular opinions
on that, except that rsync already has a ton of options and adding more just
makes that problem worse.  I'd certainly say that this should be enabled by
default and disabled only when necessary and with some sort of warning or
option.  (I have no idea if it's safe to hardlink a device if someone
-wasn't-
expecting it, but it can only happen as root...  And if you're running with
--link-dest, as root, there's already something fairly unusual going on and
I'd
argue that it's unlikely to screw a -running- system since you're making
a -new-
hierarchy that certainly isn't being used as a running system at the
time...)

Thanks again!


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