Re: [gentoo-user] Back up a server in real-time

[Alan McKinnon <alan.mckinnon@gmail.com>]

On Sunday 16 November 2008 02:08:42 Mick wrote:
> On Saturday 15 November 2008, Dale wrote:
> > Mick wrote:
> > > Without gentoo-wiki my knowledge level is rather poor (just like my
> > > memory!)
> > >
> > > What would you use to back up a running server without taking it off
> > > line?
> >
> > I keep mine simple, cp -auv paths/you/want/to/backup back/up/to  It has
> > works so far.  Thought about doing a cron job but that complicates
> > things.  :/
>
> Thank you all for the suggestions and for the link to the wiki!  I've got
> some reading to do.  ;-)
>
> Whenever I have used tar to back up a whole OS I used it with a LiveCD. 
> This was to make sure that files and their metadata were not being changed
> while I was tar'ing them.
>
> Are you saying that I can actually fire up tar/rsync and back up in real
> time?

Yes. Unix does some RealSmartThings(tm) when using files. The name is just a 
pointer to the actual file, represented by an inode. Once you have an inode 
open, it stays open until everything using it closes it. So you can 
add/delete/copy/move files by name with impunity as you then just move names 
around. Contrast this with other inferior systems, like say Windows for 
example, which has a built-in self-destruct button when you try this...

> I was gravitating towards using LVM snapshot and then tar'ing that to an
> external USB drive.

This is the preferred way, as you get a consistent snapshot frozen at a point 
in time. This deals nicely with inconsistencies caused by files changing 
while you are backing up other ones.

-- 
alan dot mckinnon at gmail dot com