Re: CUPS - how to match autodetected printers to physical ones
On Sun 26 Feb 2023 at 17:09:51 +0300, Reco wrote:
> Hi.
>
> On Sat, Feb 25, 2023 at 11:26:21PM +0000, Brian wrote:
> > > It's interesting how you bring up DHCP, yet do not mention DHCP option 9
> > > (aka "option lpr-servers" in ISC lingo).
> > > A proper implementation of DHCP options would make DNS-SD (and other
> > > assorted kludges) completely redundant.
> > > But that would be in an ideal world, and in the real world DNS-SD
> > > serves its function (within its inherent limits of course).
> > > If it works, that is.
> >
> > If the IP address changes, ipp://10.76.172.100/ipp/print as a
> > URI becomes useless. DNS-SD ensures a reachable URI. Got it?
>
> There's no need to be rude.
Apologies if it came through like that. Note that rfc7472 says
>...literal IPv4 or IPv6 addresses SHOULD NOT be used...
> Leaving aside changing printer's IP (the main question here is why would
> anyone would do it), how exactly DNS-SD helped Greg to print in that
> environment?
>From one of Greg Wooledge's previous mails:
> + eno1 IPv4 Canon LBP712Cdn (db:c0:d3)
> + eno1 IPv4 HP LaserJet P3010 Series [0FCDD7]
> + eno1 IPv4 hp LaserJet 4250 [621E13]
He did not want to use these printers, but they would be shown in
the print dialog of Evince (say), as would be the non-adverised
printer if it had been set up correctly. A click or two to print.
Alternatively, 'lpstat -l -e' and print with 'lp -d PRINTER FILE'.
> > > > It would also be hoped that port numbers and resource
> > > > paths are on the sheet of paper, otherwise a user will have a
> > > > lot of guessing to do.
> > >
> > > Nope. RTFM would suffice, as always.
> >
> > I do not think you understand my argument. A port for an IPP
> > printer need not be on 631 and the resource path need not be
> > ipp/print. RTFM hardly helps when there is an immediate need
> > to print.
>
> I wish you good luck in "convincing" typical dumb printer firmware in
> performing such feats. Bonus points for "convincing" enterprise-grade
> printer firmware to do the same.
IPP printers need not be physical printers.
> The main question here, of course, is why complicate things without the
> need?
>
>
> > RTFM? Which ones would you recommend?
>
> This one is good enough:
>
> https://www.pwg.org/ipp/ippguide.html
>
>
> > Actually, CUPS performed splendidly.
>
> If CUPS in that configuration did not allow a user to print certain
> amount of pages, then it cannot be called splendid.
CUPS did not stop a user from printing. It knew of three
printers (see above). The fourth was hidden from it.
> > The OP was on a badly set up, unco-operative network. That was (and
> > probably still is) the root of the issue.
>
> And here it's you who seem to misunderstand the issue.
> It's a city hall, or something like it. People come there, some are in
> the need of printing.
>
> We have a confirmed and documented case of CUPS failing to deliver the
> desired result (i.e. printing something) in that environment. Without
> additional user configuration, that is.
>
> Last time I've checked, they did not provide CUPS on any Android phone
> out of the box, and probably it's the same for Apple phones.
> It's likely that some visitor would bring a laptop with them, and it's
> likely that said laptop would run M$ Windoze (or whatever that
> shovelware is called these days).
> If mobile users or M$ laptop users would encounter any trouble printing
> - surely someone would make something to fix it.
>
> Yet is was not fixed (for a year at most), so it's likely *it works for
> the users*, so there's nothing to fix. Some user configuration on their
> device may be required, or not, it's not relevant here.
>
> Does that mean that CUPS is in need of fixing? Of course not.
> Does that mean that DNS-SD is not needed? Of course not.
> Does that mean that the only way of printing something via CUPS is to
> use DNS-SD? You can guess it, it's also not.
>
>
> Moreover, printing something at a city hall is a rare (although
> periodic) task. If the printer's IP changes between Greg's vistits there
> - so what?
A few quotes from Greg Wooledge's first mail:
> Whatever I managed to do last year... it's not working this
> year. I can only assume that my workplace's lovely IT
> department...
> When I tried to print this year's tax form to my local
> printer, I learned that the default print queue I had
> set up last year is no longer there.
> This led to a complete rerun of everything from last
> year...
You ask - "so what?" As can be seen, it hardly results in a happy
camper!
> > > > How would an ordinary user go on? "Give them a piece of paper" sounds
> > > > awfully like "Let them eat cake".
> > >
> > > Easy, a user should RTFM. Failing that, a user can use a different
> > > device or OS, or *gasp* - just use ipptool. Given the environment, a
> > > creative use of samba suite would probably solve the problem too, but
> > > let's not get into *that*.
> > > And there's that last step - just ask somebody.
> >
> > You welcome Big Boss into your office for a $100M deal.
>
> Nope. Either it's the "ordinary user" or it's the "Big Boss".
> Please choose one.
Big Boss represents all ordinary users. She knows printing "just
works" when set up correctly.
--
Brian.
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