Dump/Restore for system migration

[Polytropon]

On Thu, 22 Jan 2015 09:38:12 -0800, Chris Maness wrote:
> > On 2015-01-19 5:05 PM, Polytropon wrote:
> > >> Is there a better way to do this?
> > > Usually not, because dump + restore is _the_ way to do it.
> > > Except of course you're using ZFS. :-)
> > I have often done system migrations using rsync over ssh something like
> >
> > rsync -aHv / root at targethost:/
> >
> > The great thing about rsync is that is will only transfer what it needs
> > to, so the first run will take a while to get pretty much everything
> > over.  I then run a second time with a --delete switch to catch anything
> > that changed while the first run was going (A full sync of my mail store
> > can take well over 24 hours!).  The second run will go much faster,
> > depending on the size of the initial run.  Finally, I will mount RO, so
> > I know nothing is changing and run a final sync, which usually only
> > takes a couple of minutes, then light up the new system.
> >
> > If you already have a system dump/restore you could also just use rsync
> > as the final step to catch the stragglers.
> 
> That actually sounds pretty good.  The target system has been running for a
> few days source system powered off.  I am not sure if a rsync right now
> would do more harm than good.  However, I do understand that rsync will
> ignore files that have already changed.
> 
> I use rsync -vaur flags on most of my backups.

Note that it's not just about file modification. The
copying mechanism has to be able to deal with _all_
file attributes (standard file permissions, file flags,
and also specials such as symlinks and hardlinks).
With dump + restore, you definitely get an 1:1 copy,
especially when you dump from the source system
(immutable!) to a clean (empty) disk of the target
system. For transfering additional changes, rsync
is a good tool. I'd also like to mention the program
"cpdup" from the ports collection.


-- 
Polytropon
Magdeburg, Germany
Happy FreeBSD user since 4.0
Andra moi ennepe, Mousa, ...