Re: Where is data stored when Synaptic scans DVDs?
On Mon 20 Mar 2017 at 23:03:29 (+0000), Brian wrote:
> On Sun 19 Mar 2017 at 23:25:47 -0500, David Wright wrote:
>
> > On Sun 19 Mar 2017 at 08:50:55 (-0500), Richard Owlett wrote:
> > > On 03/19/2017 08:08 AM, David Wright wrote:
> > > >[snip ;]
> > > >
> > > >How's the other research coming along?
> > > >Did you see if there were files whose timestamps change?
> > > >Did you see whether you can find the files which are apparently
> > > >indexed in /var/lib/apt/cdroms.list?
> > > >And if/when you find them, what are you going to use them for,
> > > >in view of your new philosophy of working from the DVDs anyway?
> > >
> > > It's not new. People just assumed that I would do things a certain
> > > way because that would be the way they would do it.
> > > I put effort into asking narrowly focused questions.
> >
> > And I put effort into answering it as best I could.
> > The first answer to the thread may well be correct, but
> > you don't appear to have looked to see if it was correct.
>
> The question asked is clear enough. The responses are muddy. I do not
> think there is an agenda [1] here.
Perhaps you can bring some clarity to the situation.
I have merely tried to suggest some places to look for information
written by synaptic, by analogy with apt-cdrom's behaviour.
> > ...where is the data about contents of each DVD stored?
>
> > I suggested /var/lib as another possibility, partly because
> > I think it would be easier to eliminate. All the files in
> > my /var/lib/apt are plain text, so it would be hard to hide
> > the information from scanned CDs.
>
> It isn't hidden.
Good.
> > OTOH /var/cache/apt contains a couple of .bin files which
> > have package names in them. Not having CDs to scan, I can't
> > test the file timestamp idea. If they changed, it would
> > suggest Jonathan was correct, but be trickier to prove.
> > Hence checking, and possibly eliminating, /var/lib.
> > Also there's the point that those .bin files may contain more
> > than just some CD indexes, so sharing them between different
> > systems would be high-risk.
>
> I dug out my trusty set of Slink CDs [2] and popped CD1 into the cdrom
> drive.
Mine could still be hanging from threads in the vegetable plot,
scaring the birds. Too many oceans in between for me to check.
> root@gnome-stable:~# apt-cdrom ident
> Using CD-ROM mount point /media/cdrom/
> Mounting CD-ROM...
> Identifying... [312b07c10c39c9ce1e89be115088d562-2]
> Stored label: Debian GNU/Linux slink (2.1) 1/4 main binary-i386 section 1 SAM19990617
> Unmounting CD-ROM...
>
> root@gnome-stable:~# apt-cdrom add
> Using CD-ROM mount point /media/cdrom/
> Unmounting CD-ROM...
> Waiting for disc...
> Please insert a Disc in the drive and press enter
> Mounting CD-ROM...
> Identifying... [312b07c10c39c9ce1e89be115088d562-2]
> Scanning disc for index files...
> Found 4 package indexes, 0 source indexes, 0 translation indexes and 0 signatures
> This disc is called:
> 'Debian GNU/Linux slink (2.1) 1/4 main binary-i386 section 1 SAM19990617'
> Reading Package Indexes... Done
> Writing new source list
> Source list entries for this disc are:
> deb cdrom:[Debian GNU/Linux slink (2.1) 1/4 main binary-i386 section 1 SAM19990617]/ slink contrib main non-US non-free
> Unmounting CD-ROM...
> Repeat this process for the rest of the CDs in your set.
>
> A portion of the output:
>
> root@gnome-stable:~# ls -l /var/lib/apt/lists
> -rw-r--r-- 1 root root 873670 Mar 20 22:30 Debian%20GNU_Linux%20slink%20(2.1)%201_4%20main%20binary-i386%20section%201%20SAM19990617_dists_slink_main_binary-i386_Packages
>
> There we are - a complete answer to the question and a completely
> satisfied customer. :)
I hope so. But I read "Just copying /etc/apt/sources.list and
/var/lib/apt/lists is not enough" written by the OP in
https://lists.debian.org/debian-user/2017/02/msg00518.html
I reminded the OP of the mention of /var/lib/apt/cdroms.list
quoted in that email, acknowledged on 12 Feb in
https://lists.debian.org/debian-user/2017/02/msg00537.html
but the question has been raised again. Whether synaptic does
something itself that goes beyond what is done by apt-cdrom, I do not
know; nor where to find that out. Hence the suggestion to carry out
experiments, which the OP might enjoy for the experience.
Obviously the OP wants to be able to find a set of files on one system
which, when transferred to another system, will tell the latter
everything that the former knows about a set of CDs, in order that
they don't have to be rescanned on the latter system. I don't think
your demonstration here has shown that those files _are_ sufficient,
even if you were correct in thinking they are.
Cheers,
David.
Reply to: