Re: Where is data stored when Synaptic scans DVDs?
On Mon 20 Mar 2017 at 20:23:48 -0500, David Wright wrote:
> 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.
This part of my response wasn't very clear. I was thinking of
> you don't appear to have looked to see if it was correct
at the time and was wondering why the OP has let his issue hang in the
air in his responses.
The contention that
> People just assumed that I would do things a certain way because
> that would be the way they would do it.
also requires us to tailor our responses to the OP's thought processes.
That's all apart from the assumption being nonsense. The logical outcome
would be that he doesn't get any replies; it is too wearing to have
guess someone's innermost desires.
> > > ...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.
cdroms.list, sources.list and the files in lists/ are necessary. They
are the only files which change when a CD is added. Whether they are
sufficient when put on the target system is another matter.
--
Brian.
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