Rsync - does it really do an *exact* copy?

martin aa martinaa at
Mon May 29 12:09:36 GMT 2006

> On Mon 29 May 2006, martin aa wrote:
> > Hi Rsync-ers
> >
> > I'm simply using rsync to do an exact copy of my root (and home) 
> > partition by using the -aHv options.
> >
> > When the copy is complete, I modify fstab so my root and home 
> > mount points are pointing to the newly copied partitions.
> Do you also actually boot with the new root filesystem? Modifying only
> the fstab can lead to very confusing situations. Don't forget that the
> kernel has to mount the root filesystem before it can read the fstab;
> look at what is passed at boot time in the root= parameter.

Hi Paul - thanks very much for your reply.

Yes, I'm sorry, but I should have mentioned that I also modified the boot parameters to the kernel (in /boot/grub/grub.conf) to access the correct  partition for the root mount point.  So, I'm definitely confident that the new root filesystem is being booted.  (Note also that even if that were not the case, when I copied the file system back to the original partition it would work again - which, as I said in my original post, it doesn't.)

> > Just to be sure it was rsync, I completed deleted my original 
> > root and home partitions (it's okay, it was a new installation) 
> > and then copied everything back (again using the -aHv options).  
> > However, I ended up with exactly the same problem.
> I've just been busy with a new system, and I've been copying over the
> root filesystem multiple times with rsync, without any such problems
> whatsoever, so at least for me rsync works just fine for that task.

Well, that is interesting.  I'm using FC5 and, by the looks of your domain name, you're using a debian-based distro.  So, I really can't work out what is happening here.  As I said in my original post, I can't see how it could be anything other than rsync doing this, but I just can't see how.  My understanding is that by using -aH you preserve absolutely everything.  Is there some type of file that rsync just can't accurately copy?

Anyway, again, thanks for providing this info.  It will be interesting to see if anyone else has had this problem with FC5 or any other distro.  But why should the distro matter?? - all very strange!  I'm looking forward to getting to the bottom of this one.

Regards, Martin

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