BackupPC-users

Re: [BackupPC-users] BackupPC and Windows junction points

2011-02-07 13:46:38
Subject: Re: [BackupPC-users] BackupPC and Windows junction points
From: "Michael Stowe" <mstowe AT chicago.us.mensa DOT org>
To: "General list for user discussion, questions and support" <backuppc-users AT lists.sourceforge DOT net>
Date: Mon, 7 Feb 2011 12:44:51 -0600
> There was a thread a little while back warning about junction point
> and Windows Vista/7. Also, the Wikki
> (http://sourceforge.net/apps/mediawiki/backuppc/index.php?title=Common_backup_excludes)
> talks about the need to exclude Junction points to avoid duplicate
> backup trees.
>
> But it seems to me that at least when using cygwin rsync, that
> junction points are treated as symlinks so that there doesn't appear
> to be any duplication in backups.
>
> The only issue may be in restoring in that cygwin rsync won't
> distinguish between true symlinks and junction points which are
> different animals in the Windows world.
>
> Am I missing something?

I don't *think* you are -- junction points have been around since Windows
2000 or so, and are best described as a kind of limited symbolic link --
to be confusingly replaced in Vista with NTFS symbolic links (symlinks)
which are still called "junction points" for historical reasons.

These are not to be confused with "directory junctions," which was kind of
the missing piece of a symbolic link -- and NTFS *does* also do hard
links.  On the plus side, in more recent versions of NTFS, although the
implementation ultimately is reparse point weirdness, behaves pretty much
like POSIX symbolic and hard links.

I'll whang together a chart:
POSIX          |   Windows 7          | Older Windows
-----------------------------------------------------
symbolic link  | soft link or symlink | junction point/directory junction
hard link      | hard link            | hard link

Last I checked, cygwin/rsync/tar treated modern Windows symbolic links
sanely, and treated hard links like unrelated copies of the same file. 
I'm not sure if this is still the case or what the ramifications are for
recovery.

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