Is there a howto/tutorial on backups/rsync that covers the use of hard and soft links?

[François]

Hi Joe,

If you want to understand hard-links, just take a look at Wikipedia :
http://en.wikipedia.org/wiki/Hard_link#Example

I think it's pretty easy to understand.

To understand how hard-links (and rsync) can help you make strong incremental 
backups, head over
http://blog.interlinked.org/tutorials/rsync_time_machine.html

Cheers,

-- 
François


Le mardi 22 janvier 2013 23:12:38, Joe a écrit :
> Thanks for the reply.  I know what hard and soft links are and have some
> idea of how they relate to backup.
> 
> What I need is a tutorial on how all of that works with rsync.  I can
> see that there are a lot of considerations as to which options to use
> for different situations and maybe some general strategies on how to
> build something like an incremental  or differential backup.
> 
> I use rsync now on a one directory tree to one directory tree basis now,
> but I'd like to have more than one backup on my backup device without
> doubling the storage which is what hard links will help me do once I
> know how they work in more detail.
> 
> Joe
> 
> On 01/22/2013 02:48 AM, Tony Abernethy wrote:
> > This may help:  (man ln)
> > 
> > A hard link to a file is
> > indistinguishable from the original directory entry; any changes to a
> > file are effectively independent of the name used to reference the file.
> > Hard links may not normally refer to directories and may not span file
> > systems.
> > 
> > Assuming you do many backups and many of the files do not change,
> > hard links are your friend.
> > 
> > Backing up soft links:
> > Do you back up the link or what the link points to?
> > (Even that simple thing has interesting ways to get complicated.)
> > 
> > -----Original Message-----
> > From: rsync-bounces at lists.samba.org
> > [mailto:rsync-bounces at lists.samba.org] On Behalf Of Joe Sent: Tuesday,
> > January 22, 2013 1:32 AM
> > To: rsync at lists.samba.org
> > Subject: Is there a howto/tutorial on backups/rsync that covers the use
> > of hard and soft links?
> > 
> > There have been a lot of posts on the list lately about issues with hard
> > links.  It has been very interesting, but I don't understand it very
> > thoroughly.  I haven't used hard links for anything yet.  I've used
> > symlinks - not for backups, of course - and have seen them get broken or
> > deleted in backups.
> > 
> > Is there a tutorial anywhere that will explain how this works (assuming
> > that the reader understands the basic concepts of backups and knows how
> > to program, but doesn't really understand how to use links to create
> > things like incremental or differential backups)?  It seems like there
> > are a lot of fine points to consider, some of which can really bite you
> > if you don't take them into account.
> > 
> > I'm working on my own personal backup system using bash and rsync.  When
> > it's done it will be pretty good, but it would be *much* better if I
> > rewrote it to have more backup versions using hard links to save space.
> > 
> > I am writing my own because (aside from learning a lot) I have only seen
> > two types of backup utilities - those that are very simplistic and won't
> > let me do what I want and those which are enterprise level and I can't
> > figure out how to get them to do anything without extensive study.  (I
> > did experiment with areca (I think it uses rsync libraries under the
> > hood) which would probably do everything I want, but I got stuck too
> > many times and couldn't get enough support on their forum to keep
> > going.)
> > 
> > TIA
> > 
> >     Joe
> > 
> > --
> > Please use reply-all for most replies to avoid omitting the mailing list.
> > To unsubscribe or change options:
> > https://lists.samba.org/mailman/listinfo/rsync Before posting, read:
> > http://www.catb.org/~esr/faqs/smart-questions.html