Re: Interrupted backups

[Colin Percival <cperciva@tarsnap.com>]

On 03/21/14 08:13, John Gamble wrote:
> Thanks again for your reply.  Still slightly confused about this process
> though….  In the scenario I'm thinking about, 'backup-wednesday.part' and
> 'backup-thursday' wouldn't have any common files (or blocks of data).  The
> complete archive would be the sum of 'backup-wednesday.part' and
> 'backup-thursday'.

What "common archive" are you talking about here?  If you mean "the archive
you're creating on Thursday", that's the 'backup-thursday' archive I was
talking about, and any blocks from Wednesday which are needed will be included
in that archive automatically.

>  Therefore, how is it possible to delete
> 'backup-wednesday.part'?  Is it, in fact, impossible to do so in this case?  If
> so, is there any way to create a single complete backup/archive from two or more
> partial ones, that were formed by premature termination of a backup.

You *can* merge two archives together, but I don't think that's what you want to
do here.  You can just tell tarsnap to create an archive with all of the data
you want it to have, and it will magically pull in bits of previous archives as
needed.

> I'm asking all this because given the speed of my upload connection, I know that
> I'll have to stop the initial backup before it completes.  Just wanted to make
> sure that I'll ultimately be able to create a complete backup.

Assuming that you don't have more "new" data each day than you have bandwidth,
yes.  Just tell Tarsnap to create a backup with all of your data each day, and
then stop it when you need to.  If you have 1 GB/day of bandwidth, you'll end
up with a 1 GB archive on Monday, a 2 GB archive on Tuesday (of which 1 GB was
uploaded new and 1 GB was reused from Monday), a 3 GB archive on Wednesday (of
which 1 GB was uploaded new and 2 GB was reused), etc. until you finally have
a single archive containing all of your data.

> 1).  To terminate an ongoing backup, is the command ^Q?

Ctrl-Q into the terminal session where you're running tarsnap, or you can send
a SIGQUIT signal (which is what Ctrl-Q translates into).

> 2).  While the backup is ongoing, is it OK to use the computer as normal?

Of course.  UNIX is designed for multitasking. ;-)

-- 
Colin Percival
Security Officer Emeritus, FreeBSD | The power to serve
Founder, Tarsnap | www.tarsnap.com | Online backups for the truly paranoid