Printing from the phone

[Till Kamppeter]

Hi,

I have a Nexus 4 now to test the printing stack on the phone.

First I have updated the USB-connected phone to the development branch 
of the OS via

ubuntu-device-flash touch --channel=devel

with the phone booted into Ubuntu and the screen unlocked.

After the reboot of the phone I have run

phablet-config writable-image

to be able to install packages with apt-get and entered a shell on the 
phone via

phablet-shell

In the shell I first installed a level-1 printing stack (See 
https://blueprints.launchpad.net/ubuntu/+spec/client-1305-printing-stack-with-mobile-in-mind 
for the levels):

sudo apt-get install cups-daemon cups-browsed avahi-daemon

This makes the following new packages getting installed:

The following NEW packages will be installed:
   avahi-daemon bc bind9-host cups-browsed cups-daemon libavahi-core7
   libavahi-glib1 libbind9-90 libcupsmime1 libdaemon0 libdns100 libgeoip1
   libisc95 libisccc90 libisccfg90 liblwres90 libpaper1 ssl-cert
0 upgraded, 18 newly installed, 0 to remove and 0 not upgraded.
Need to get 1,502 kB of archives.
After this operation, 4,698 kB of additional disk space will be used.

The installation was hanging on the postinst of CUPS, so I had to open a 
new shell in another terminal and kill the postinst for the installation 
process to finish.

sudo apt-get install -f

has re-run the CUPS postinst and this time it finished.

As the phone apps do not yet have a print dialog I needed a print client 
on the phone, and also some tools for developing and debugging. So I 
have installed cups-client, giving me command line printing and print 
admin commands, as lp, lpstat, lpinfo, lpadmin, ...:

sudo apt-get install cups-client
[...]
The following NEW packages will be installed:
   cups-client cups-common libcupsfilters1 libcupsimage2
0 upgraded, 4 newly installed, 0 to remove and 0 not upgraded.
Need to get 368 kB of archives.
After this operation, 2,810 kB of additional disk space will be used.

PID 1 on the phone is still Upstart, Upstart is configured to start CUPS 
on-demand, via

/etc/init/cups.override

cups.override needs to be corrected, as cupsd does not support the "-x" 
option any more, so I have removed the "-x 30" from the cupsd command 
line. Now cupsd starts when running commands like

lpstat -r
lpstat -v
...

After that I did

sudo start cups-browsed

to start cups-browsed to get the queues from remote CUPS servers locally 
available (level 1 printing stack).

lpstat -v

shows my printers shared on remote CUPS servers now.

Note that CUPS admin tasks need "sudo" as the "phablet" user is not in 
the "lpadmin" group.

For the printing tests I do the CUPS logging (in 
/var/log/cups/error_log) in debug mode, running

sudo cupsctl --debug-logging

sudo cupsctl

shows my settings.

Now I print via

lp -d printer ~/.bashrc

CUPS is now supposed to send the job via IPP (Internet Printing 
Protocol) to the remote CUPS server where the printer is actually 
connected to. This it does using a backend, a small helper program, in 
our case /usr/lib/cups/backend/ipps.

Printing does not work yet:

1. CUPS reports exit status 127 on the ipps backend call (command not 
found, the fact that in error_log you see "file too large" is a CUPS 
bug, exit status 127 is command not found), but the backend is called 
with its full path, the backend is actually present and executable, no 
libs missing (checked with "ldd"), the backend works directly called 
from the command line.

2. No name resolution in the local network (avahi problem? avahi-daemon 
is running). Manual call of the backend only works if the host name in 
the device URI is replaced by the corresponding IP address.

So following command prints:

DEVICE_URI=ipps://192.168.0.11:631/printers/printer 
CONTENT_TYPE=text/plain /usr/lib/cups/backend/ipps 1 1 1 1 "" ~/.bashrc

Also

sudo DEVICE_URI=ipps://192.168.0.11:631/printers/printer 
CONTENT_TYPE=text/plain /usr/lib/cups/backend/ipps 1 1 1 1 "" ~/.bashrc

prints.

Has someone of you any idea how to solve the two mentioned problems, the 
"command not found" if the backend is called from within CUPS and the 
host name resolution not working.

Any help is much appreciated.

    Till