Re: Identifying which files changed between archives

[Colin Percival <cperciva@tarsnap.com>]

Hi Scott,

On 2019-06-18 04:49, Scott Dickinson wrote:
> I'm trying to work out how to generate a report on files that are new or
> changed in a particular archive. I can't seem to find an easy way to do this,
> so hoping someone can help.
> 
> Here is the scenario I'm working through.
> 1. Backup directory "x" on 1st May 2019. First time archive, all 10Gb are sent
> as expected.
> 2. Backup directory "x" on 1st June 2019. Second time archive, 25Mb are sent.
> 
> How can I report on which files that 25Mb of delta's are part of? In this
> scenario, I wasn't expecting any changes to the files over the month, so am
> surprised there were anything above the metadata to be backed up. My
> understanding is that Tarsnap needs to know which files the changed blocks
> belong to, therefore in theory this metadata should be extractable.

Not exactly.  At one level Tarsnap knows which blocks are part of each file,
but that's not the same thing as knowing which file a block comes from --
that isn't even a completely meaningful question, since a block might occur
in multiple files or in no files (if it's a block of metadata).

> The closest I've found to locate this is "tarnsap -t -f 'x' -v --iso-dates",
> but this doesn't natively provide the details I'm after. Ideally I'd like
> tarsnap to be able to report which files were uploaded at the time or archive
> with an option similar to --print-stats.
> 
> Anyone got any ideas?

The best I can suggest is to use `tarsnap -tv` to list each archive and
compare the output from the two runs.

-- 
Colin Percival
Security Officer Emeritus, FreeBSD | The power to serve
Founder, Tarsnap | www.tarsnap.com | Online backups for the truly paranoid