On Fri, 5 Jul 2019 at 14:18, Steve Mynott <steve.mynott@gmail.com> wrote:
> dpkg -S doesn't use the network.

Sorry, my question was badly worded.

By offline I mean that I won't have the system booted, but will be
looking at a backup of the files on a different computer.

(Eg: Remove SD card from Raspberry Pi, insert into my desktop
(Ubuntu), and look at the files on the SD card to determine what
packages were installed.)

The actual use case is to compare tarballs taken from multiple Pis to
see what changes between archives. On a complete OS backup a lot of
files will have changed, but the vast majority of them are OS files
that can be accounted for by a handful of packages. So for example I
don't want to know that one backup has /usr/bin/411toppm,
/usr/bin/anytopnm, /usr/bin/asciitopgm, etc in it but the other
doesn't, I want to say that the first backup had netpbm installed bu
the second didn't. (netpbm is just one example: its .deb alone
comprises 486 files, so installing it one unit creates 486 file
differences that can be accounted for by that one package install;
scale that up to an entire O/S...)

Since I've expanded on this I'll add: ideally I want to do as much as
possible from just the file listing that I get from tar -jt to avoid
extracting multi-GB files to do the comparison. Hence specifically
wanting to map "/usr/bin/411toppm" to "netpbm" by the filename/path
alone.

--
Mark Rogers // More Solutions Ltd (Peterborough Office) // 0844 251 1450
Registered in England (0456 0902) 21 Drakes Mews, Milton Keynes, MK8 0ER

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