Re: Interrupted backups

Dear Colin,

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'. 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.

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.

A couple of minor queries:

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

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

Thanks again and apologies for the continued questions.

Regards,

John Gamble

###

On 20 Mar 2014, at 22:23, Colin Percival <cperciva@tarsnap.com> wrote:

Hi John & list,

On 03/20/14 07:21, John Gamble wrote:
a). The archive 'backup-thursday' will contain only those files not present in
'backup-wednesday.part'

Sort of. The Tarsnap service doesn't have any concept of "archives". When you
create backup-thursday, tarsnap will upload the blocks of data needed by
backup-thursday which are not present in earlier archives.

b). If I delete 'backup-wednesday.part', then all the files necessary to create
the complete backup (in this case, all the files) will be retained and
transferred to 'backup-thursday'. So 'backup-thursday' is now a complete backup.

There's no "transferring" going on; but tarsnap will only delete the blocks
which are used by the deleted archive and not by any of the archives you're
keeping. (Keeping track of this is what the cache directory is for.)

c). To delete 'backup-wednesday.part', the command would be 'tarsnap -d -f
backup-wednesday.part'.

Correct.

The reason I'm querying this is that you mention
something about having 'delete keys'. Could you clarify this please? I don't
see anything about a requirement for that on the Tarsnap general usage page, in
the section relating to deleting archives.

When you create a set of keys using the tarsnap-keygen utility, you get a key
file which has all of the keys for that machine. But you can use the
tarsnap-keymgmt utility to create a key file which has only a subset of keys, e.g.,
one which can be used to create archives but can't delete them.

But that's "advanced usage" and not something you need to worry about at first.

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

--------------------

John Gamble

Senior Computer Biologist
Cancer Genome Project
Wellcome Trust Sanger Institute
Cambridge, UK
CB10 1SA

Tel: +44 (0)1223 - 834244
Ext: 7703
jg5@sanger.ac.uk

-- The Wellcome Trust Sanger Institute is operated by Genome Research Limited, a charity registered in England with number 1021457 and a company registered in England with number 2742969, whose registered office is 215 Euston Road, London, NW1 2BE.