Re: An INCOMPLETE solution - was [Re: Where is data stored when Synaptic scans DVDs?]
On 2017-03-28, David Wright <deblis@lionunicorn.co.uk> wrote:
> On Sun 26 Mar 2017 at 11:31:57 (+0000), Curt wrote:
>> On 2017-03-25, David Wright <deblis@lionunicorn.co.uk> wrote:
>> > On Sat 25 Mar 2017 at 10:50:50 (+0000), Curt wrote:
>> >> Actually, srcpkgcache.bin includes the information contained in the files
>> >> in /var/lib/apt/lists; that is, all the info you obtain from the internet
>> >> via your deb and deb-src lines -- this information changes only on
>> >> apt-get update.
>> >>
>> >> pkgcache.bin caches the information in srcpkgcache.bin + the information
>> >> extracted from the apt and dpkg status files. This info changes on every
>> >> install/remove done by apt or directly by dpkg.
>> >>
> You can also see from the head of the file that the most of the
> "versions" are not the versions of the packages but are actually
> constraints, ie dependencies/replacements/breakages etc. all just
> jumbled up.
Well, I actually checked further down than the head (let's refer to it
as the body) and I did systematically discover version and package
names, so I think the output is more coherent than you're letting on but
who cares? We know what is in those files (thank you David #1--yes I'm
relegating you to David #2, sorry). That is the point of my post in the
first place. It is not true what you posited, that it is tricky to know
what those files contain. We know (although it is not documented in the
man page(s) because people in the know figure these descriptions too
low-level for mortals like us. Maybe therein lies the trickiness.
> Within this jumble, I think it would be difficult to unambiguously
> locate information that was specific to apt-cdrom or synaptic, were
> either of these to add information not covered by your reference.
>
> $ ls -l /var/cache/apt/srcpkgcache.bin
> ... 22531192 Mar 27 21:00 /var/cache/apt/srcpkgcache.bin
> $ strings /var/cache/apt/srcpkgcache.bin | wc -c
> 3655511
> $
> so the output of strings amounts to about 16% which means that
> 84% could be "hiding" other information from our eyes.
>
> I've never looked at (let alone examined) these files after scanning
> CDs with synaptic (assuming these same filenames are used), so I have
> no idea whether they contain the same information as apt-get update
> writes, or more. And as for what man apt-cdrom means by
> "correcting for several possible mis-burns", I have no idea.
They contain exactly what David #1 said they did, I assume, as I have no
good reason not to believe him (given that he's a bona fide authority on
the matter in his role as an APT contributor).
But in the context of the OP why you couldn't copy the two files from
the first machine after the cds had been scanned and then copy them back
to the second machine in order to avoid rescanning I don't know.
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