Mystery printer in firefox under Ubuntu 14.04.5

[Brian]

On Thu 16 Mar 2017 at 10:48:35 -0400, Robert Heller wrote:

> At Thu, 16 Mar 2017 11:40:05 +0000 "Ubuntu user technical support,  not for general discussions" <ubuntu-users at lists.ubuntu.com> wrote:
> 
> > 
> > On Wed 15 Mar 2017 at 17:36:18 -0400, Robert Heller wrote:
> > 
> > > For some unknown reason a "mystery" printer is showing up in FF's selection of
> > > printers. This printer does NOT show up in 'lpstat -t'. It is not in
> > > /etc/cups/printers.conf. And I know for sure that I uninstalled the (stupid)
> > > deamon that finds new random printers (don't need or want that sort of "user
> > > friendliness"). Is this a Ubuntu issue or a Firefox issue or a Unity/Gnome
> > > issue? I have not seen this on my CentOS machines, ever. It only seems to
> > > happen on the diskless Ubuntu machines I set up using DRBL.
> > 
> > Please post
> > 
> > 1. The entry for this printer in Firefox's print dialog.
> 
> Don't have the exact thing right now -- the machine in question is not powered
> up right now and I am not presently at the library. It is something like
> "NPI76<more digits>"
 
My HP LaserJet has a default hostname which begins "NPI".
 
> > 2. The name of the "(stupid) deamon".
> 
> cups-browsed
> 
> This daemon is (I guess) meant to be helpful (?) on a laptop that 'roams'
> about and it seems to find new printers and/or remove printers that are no
> longer available. We don't want / need this on *hard (network) wired*
> workstations with a pair of *hard (network) wired* printers.  We don't want 
> printers coming and going automagically.

cups-browsed is also useful for machines which do not roam but, as you
say, you have no need of it. Without it the cups daemon will only see
the local print queues you have configured on a machine. They are in
printers.conf and shown by 'lpstat -t'.

> > 3. The outputs of
> > 
> > 	/usr/sbin/lpinfo -v
> > 	lpstat -t
> > 	systemctl status avahi-daemon.service
> 
> 
> On the Ubuntu VM server (serves the /tftpboot of the kernel, the root and /usr 
> file systems to the PXE booting diskless workstations):

[Snip]
 
> network dnssd://hp%20LaserJet%204200%20(0001E67659FE)._pdl-datastream._tcp.local/

This is a URI for the LaserJet 4200. The machine it is connected to is
running CUPS and doing Bonjour broadcasting. You have not used this URI
to set up a print queue for the printer.

> ub140464.wendellfreelibrary.org% lpstat -t
> scheduler is running
> system default destination: BrotherColorLaser
> device for BlackandWhiteLaserjet: ipp://192.168.1.251:631/printers/BlackandWhiteLaserjet

This is the URI you have used to set up a print queue for the Laserjet
4200.

> device for BrotherColorLaser: socket://192.168.1.252

Looks like you are sending print jobs directly to the MFC-9970CDW.

> BlackandWhiteLaserjet accepting requests since Sat 27 Sep 2014 05:47:52 PM EDT
> BrotherColorLaser accepting requests since Fri 05 Dec 2014 04:03:05 PM EST
> printer BlackandWhiteLaserjet is idle.  enabled since Sat 27 Sep 2014 05:47:52 PM EDT
> printer BrotherColorLaser is idle.  enabled since Fri 05 Dec 2014 04:03:05 PM EST
> 
> There is no systemctl.  The machines are not running systemd, they are Ubuntu 
> 14.04.5 and using upstart.

I was only after whether you had avahi-daemon running on the network,
The dnssd URI indicates you have.

> I will get the exact info from one of the workstations later today.
> 
> > 4. The makes/models of printers on the network.
> 
> HP LaserJet 4200
> Brother MFC-9970CDW
> 
> > We assume you have a wireless-enabled network.
> 
> There is wireless, but all of the workstations are hard wired and none have 
> wireless.  Both printers are hard wired.  One printer does not have wireless 
> (the *old* HP B&W LaserJet) and the other has the wireless turned off.
> 
> The Ubuntu "server" is running as a VM on a CentOS 6 machine.  The CentOS 6 is 
> the main file server (/home) and is also the DNS, DHCP, and LDAP server.  It 
> is also the network print server (or at least tries to be).  Both the Ubuntu 
> "server" and the CentOS 6 machine provide tftp and nfs services.

cups-browsed browses Bonjour broadcasts of remote print queues and
printers and sets up local queues for them. cupsd sees these queues and
displays them in an app's print dialog. Stopping or uninstalling
cups-browsed means remote print queues or printers will not be visible
in dialogs **via the agency of cupsd**.

However, the GTK printing subsystem is capable of browsing Bonjour
broadcasts all by itself, without the need for cupsd. This is what you
are observing when you see the extra print queue. Examining the output
of

 avahi-browse -art | less

should show the culprit. Does it?

-- 
Brian.