Re: resuming backups

[Michael Stevens <mstevens@etla.org>]

On Wed, Jul 07, 2010 at 01:02:59PM -0700, Colin Percival wrote:
> On 07/07/10 05:45, Michael Stevens wrote:
> > Question I've been wondering about: I want to backup a lot of data from
> > a machine with a slow and sometimes unreliable net connection. So I may
> > lose the net connection while backups are being created, especially the
> > initial one.
> > 
> > Is there a sensible way to resume an incomplete backup?
> 
> No.  Tarsnap doesn't do that.  What you want to do instead is keep the
> incomplete backup as a partial archive, then create a new (complete) archive.
> 
> Partial archives can be created in a number of ways, but the approach which
> matters in this context (unreliable network connectivity) is checkpointing
> using the --checkpoint-bytes option (as Johan Brinch pointed out).  This will
> ensure that if/when your backup job dies due to a lack of network connectivity
> the progress (up to the last checkpoint) will be saved as a partial archive.
> 
> When you subsequently create a new archive, Tarsnap will recognize when data
> it is processing is identical to previously-uploaded data -- including data in
> the checkpointed archive -- and will only upload the new data.

Thanks, I'm trying this. Is there any way to check if I'm creating
partial archives successfully? They don't show up with --list-archives.

Michael