Re: [Duplicity-talk] Create full backup from incremental

[Eric O'Connor]

On 2015-04-19 7:34, address@hidden wrote:
> obviously a misunderstanding. he means recreating a synthetic full
> from an existing remote chain (full+incr's).  to do that w/o using the
> local data you will have to locally recreate the latest states which
> essentially is a local restore which in turn means transfer of the
> complete chain (volumes are not cached locally).

Hmm, I think you are right about the misunderstanding, but what you say 
after that is not what I was proposing, so I'll try to explain with an 
example:





On the server:

- full-1.volume containing {FileA, FileB}
- incr-1.volume containing {FileB..now diff}
- incr-2.volume containing {FileC added}

Locally:

- Files FileA, FileB, and FileC are stored in the user's home directory
- Metadata noting FileB and FileC have changed since the last full



Then you can compute locally that a new synthetic full can be 
represented as:

synthetic-1.volume containing {link:full-1.volume[FileA], FileB, FileC}

To recover from this, the client would download "synthetic-1.volume", 
extract FileB and FileC, follow the link to "full-1.volume", download it 
and then extract FileA.


-- time passes --

If FileA is later modified, and a new FileD is added, we have:

On the server:

- full-1.volume containing {FileA, FileB}
- incr-1.volume containing {FileB..now diff}
- incr-2.volume containing {FileC added}
- synthetic-1.volume containing {link:full-1.volume[FileA], FileB, FileC}

Locally:

- Files FileA (modified), FileB, FileC and FileD (new) are stored in the 
user's home directory

So now the next synthetic backup can be represented as:

synthetic-2.volume containing {synthetic-1.volume[FileB], 
synthetic-1.volume[FileC], FileA, FileD}

To recover from this, the client downloads "synthetic-2.volume", 
extracts FileA and FileD, follows the link to "synthetic-1.volume", 
downloads it, and extracts FileB and FileC.