Re: [Duplicity-talk] Duplicity and put only backend permissions

[edgar . soldin]

ok, in conclusion that would mean that resume will build a potentially 
partially uploaded volume and try to upload it. if there is already a file with 
the same name, if only partial, the backup will fail in case it cannot  
overwrite mentioned file.

that would mean the initial idea of a write once backend would require a 
possibility to disable resuming, which are potentially doomed to fail.

..ede/duply.net

On 24.04.2015 13:24, Kenneth Loafman wrote:
> No, that's not what I meant.  When duplicity resumes, it looks at the 
> manifest.  If the volume is in the manifest, it's assumed to have uploaded.  
> If not, it restarts at the next volume.  Whatever volume may have been 
> partially built (in temp space), or uploaded (partially), will be ignored.
> 
> ...Ken
> 
> 
> On Fri, Apr 24, 2015 at 5:04 AM, <address@hidden <mailto:address@hidden>> 
> wrote:
> 
>     so resumes only happen on local incomplete volumes? but not if an upload 
> was interrupted?
> 
>     on a sidenote: retrying uploads will of course fail as well with 
> Christian's approach.
> 
>     ..ede
> 
>     On 24.04.2015 11 <tel:24.04.2015%2011>:50, Kenneth Loafman wrote:
>     > It would only be able to resume by rewriting and resending the 
> incomplete volume and continuing from there.  The upload part is in a 
> temporary volume and is not saved.
>     >
>     > ...Ken
>     >
>     >
>     > On Fri, Apr 24, 2015 at 4:00 AM, <address@hidden 
> <mailto:address@hidden> <mailto:address@hidden <mailto:address@hidden>>> 
> wrote:
>     >
>     >     On 23.04.2015 18:13, Christian Saga wrote:
>     >     > Hi there,
>     >     > I was just thinking about a new setup. Basically allowing 
> duplicity to only write new objects to S3 and not allow deletion of old items.
>     >     > This would allow me to have the backups secured, in case the 
> server gets hijacked.
>     >     >
>     >     > Do you know if this would pose problems with duplicity?
>     >
>     >     it should not
>     >
>     >     >I feel, it is only writing new objects for full and incremental 
> backups to s3. Only the purge would delete old versions? If I would turn the 
> purge off, then it should work?
>     >
>     >     the purge would either fail or succeed, but in reality not have 
> done anything depending of the implementation in the backend code. either way 
> not an issue according to your write only strategy.
>     >
>     >     > Or is there any other action, that would need the possibility to 
> change files in the backend instead of just uploading?
>     >     >
>     >
>     >     be aware of interrupted uploads. currently duplicity might try to 
> resume a backu0p and in turn overwrite a volume on the backend, which would 
> defeat your purpose.
>     >
>     >     Ken: what does happen if the upload part during a resumed backup 
> fails? would duplicity fail but try resuming again on the next run?
>     >
>     >     ..ede/duply.net <http://duply.net> <http://duply.net>
>     >
>     >
> 
>