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

[edgar . soldin]

;).. we did (talk) years ago, when the resuming was considered new and unsafe, 
but it was never implemented.. ede

On 24.04.2015 16:57, Kenneth Loafman wrote:
> I could have sworn we had a --no-resume option.  We probably just talked 
> about it.
> 
> ...Ken
> 
> 
> On Fri, Apr 24, 2015 at 8:37 AM, <address@hidden <mailto:address@hidden>> 
> wrote:
> 
>     not exactly.
> 
>     you will not be able to resume or retry, but provided your connection is 
> good and you can afford the traffic you'll have a one shot backend, where
>     - you'll start a new backup on every run*
>     - a hacked source cannot destroy/manipulate your older backups
> 
>     ..ede
> 
>     * (you will still need a way to disable resuming in duplicity)
> 
>     On 24.04.2015 15 <tel:24.04.2015%2015>:20, Kenneth Loafman wrote:
>     > I guess that's right.  If they could not overwrite, they probably could 
> not delete either, so kinda useless as a target.
>     >
>     > On Fri, Apr 24, 2015 at 7:24 AM, <address@hidden 
> <mailto:address@hidden> <mailto:address@hidden <mailto:address@hidden>>> 
> wrote:
>     >
>     >     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 <http://duply.net> <http://duply.net>
>     >
>     >     On 24.04.2015 13 <tel:24.04.2015%2013> <tel:24.04.2015%2013>: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> <mailto:address@hidden <mailto:address@hidden>> 
> <mailto:address@hidden <mailto:address@hidden> <mailto: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> <tel:24.04.2015%2011> 
> <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>> 
> <mailto:address@hidden <mailto:address@hidden> <mailto:address@hidden 
> <mailto:address@hidden>>> <mailto:address@hidden <mailto:address@hidden> 
> <mailto:address@hidden <mailto:address@hidden>> <mailto: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> 
> <http://duply.net> <http://duply.net>
>     >     >     >
>     >     >     >
>     >     >
>     >     >
>     >
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