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Re: problem adding cups print queue to debian live starting with buster

On Tue 29 Oct 2019 at 15:11:18 +0000, Drew Arnett wrote:

> Not exactly cross purposes.  I'm encountering the cups error before I
> get the chance to even select any specific printer or printer
> interface.

I had realised what was going on. My inquiry was a gentle one because
I thought there would possibly be a way round the problem, depending
on the printer model. It doesn't matter now because the issue is not
ammenable to being tackled in this way (please see below).

>             Given that this is with Debian live[1], I'll be using it,
> as I have in the past, with USB or network printers or even a parallel
> port printer if I have one.  The test setup I have right now for
> reporting on and researching this problem has both USB and network
> printers available.  The PC looks like it has a parallel port and I do
> have a parallel port printer nearby if that helps.  I definitely would
> like to figure out what's wrong, as Debian live is a useful tool, and
> it was great when printing worked with it.  (I don't care if it's a
> real bug or just a dumb user mistake to figure out and share.)

I do not think it is a user mistake. But (see below) Debian live does
not seem to have kept up with changes in buster.

> The computer, printer, and network haven't changed since this was
> working with the last Debian 9 point release XFCE live image.
> Let me walk through the scenario again, with a more step by step
> detail.  (And please ask if I should flesh out anything even further!)

Your attention to detail makes the issue easy to follow.

> Step 1:  Boot debian-live-10.1.0-amd64-xfce.iso[2].  (Image written to
> read only thumb drive.  Thumb drive read back to verify checksum and
> image integrity.)  Packages in this image are listed in [3].
> Step 2:  sudo apt-get update
> Note:  no sudo apt-get upgrade this time just to keep it simple.

Upgrading is generally not a bad move.

> Note:  sources.list only contains one line:  deb
> http://deb.debian.org/debian/ buster main

> Step 3:  sudo apt-get install cups
> Note:  cups server was not installed, so need to install.  Same with
> Debian 9 live.  Additional packages apt-get installed are in [3].
> Could there be something else required?

No printing system on Debian live? Deary me! It should be there and
functional. Why make users jump through hoops to print?

> Step 4:  sudo /etc/init.d/cups start

'sudo systemctl start cups' here. And, in addition, cups should be
started when cups-daemon is installed. I am beginning to wonder what
Debian live is playing at.

> Note:  no custom configuration changes before starting cups server.
> Wasn't required for Debian 9 live.

And should never be required.

> Note:  at this point, cups has 8 lines in /var/log/cups/error_log.
>      E [29/Oct/2019:14:40:35 +0000] Unable to open
> \"/usr/share/cups/mime\": Permission denied
>      E [29/Oct/2019:14:40:35 +0000] Unable to open \"/etc/cups\":
> Permission denied
>      E [29/Oct/2019:14:40:35 +0000] Unable to open
> \"/usr/share/cups/mime\": Permission denied
>      E [29/Oct/2019:14:40:35 +0000] Unable to open \"/etc/cups\":
> Permission denied
>      E [29/Oct/2019:14:40:35 +0000] cupsdLoadBanners: Unable to open
> banner directory "/usr/share/cups/banners": Permission denied
>      E [29/Oct/2019:14:40:35 +0000] Unable to open spool directory
> "/var/spool/cups": Permission denied
>      E [29/Oct/2019:14:40:35 +0000] Unable to open directory
> "/var/spool/cups/tmp" - Permission denied
>      E [29/Oct/2019:14:40:35 +0000] Unable to open directory
> "/var/cache/cups" - Permission denied
> Those look dire.  New with buster?

I think this is the crux of the issue. apparmor is now installed by
default. See what the journalctl output gives you.

> ls -ld on those directories shows:
>      drwxr-xr-x 2 root root 240 Oct 29 14:40 /usr/share/cups/mime
>      drwxr-xr-x 5 root lp 220 Oct 29 14:40 /etc/cups
>      drwxr-xr-x 2 root root 180 Oct 29 14:40 /usr/share/cups/banners
>      drwxrwx--T 2 root lp 40 Aug 21 07:43 /var/spool/cups/tmp
>      drwxrwx--- 3 root lp 80 Oct 29 14:40 /var/cache/cups

Nothing wrong there AFAICT.

> Note:  at this point, cupsd process is running as root.
> Step 5:  XFCE menu:  Applications:  Settings:  Print Settings
> ps -efd | grep user | grep print suggests that starts:
>      user      1125   987  0 02:37 ?        00:00:02 /usr/bin/python3
> /usr/share/system-config-printer/applet.py
>      user      6263  1075  2 14:47 ?        00:00:01 /usr/bin/python3
> /usr/share/system-config-printer/system-config-printer.py
> Note:   The dialog box for the print settings comes up ok.  There is a
> cupsd access log message showing the connection made without error.
> Step 6:  In the print settings application, click on add printer.  It
> asks for username & password authentication.  It did not do this with
> buster 9.  Cancel.
> Note:  is there a new need for user to be member of lp or lpadmin
> group?  user is member of neither.

You are using system-config-printer. Please see


> Step 7:  sudo adduser user lp

A security risk. That user can now read what I send to the printing

> Step 8:  sudo adduser user lpadmin
> Step 9:  logout and back in.  Verify user now member of those groups as well.
> Step 10:  start prnt settings application again.  Select add printer.
> Note:  no longer get the request to authenticate.  However, now get an
> error dialog popup that says:
>      "CUPS server error
>       There was an error during the CUPS operation: 'Internal Server Error'."
> With cancel & retry buttons.

Probably a consequence of having apparmor on the system.




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