Re: Interrupted backups

[Colin Percival <cperciva@tarsnap.com>]

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