CUPS service not working, can't find any logs

Question

I am running Ubuntu 14.10 and when I open up the Printers dialog, I get an error message "Printing service not available. Start the service on this computer or connect to another server".

The start service button is greyed out.

I have tried

$ sudo service cups start
start: Job is already running: cups

Followed by

ps -ef|grep cups | grep -v grep
root      1210     1  0 08:15 ?        00:00:03 /usr/sbin/cups-browsed

I've tried to find some information in the logs about this, but the logs haven't been touched for days (and they are zero bytes)

ls -t -l
total 96
-rw-r----- 1 root lpadmin    0 Jan  3 08:45 access_log
-rw-r----- 1 root lpadmin    0 Jan  3 08:45 page_log
-rw-r----- 1 root lpadmin 7920 Jan  2 13:22 access_log.1
-rw-r----- 1 root lpadmin 3389 Jan  2 13:17 page_log.1
-rw-r----- 1 root lpadmin  125 Dec 31 09:20 access_log.2.gz
-rw-r----- 1 root lpadmin    0 Dec 31 08:29 error_log
...

Only other clue I've found is the following repeated many times in dmesg

[17169.471390] audit: type=1400 audit(1421413284.183:1700): apparmor="STATUS" operation="profile_replace" profile="unconfined" name="/usr/lib/cups/backend/cups-pdf" pid=26540 comm="apparmor_parser"
[17169.471398] audit: type=1400 audit(1421413284.183:1701): apparmor="STATUS" operation="profile_replace" profile="unconfined" name="/usr/sbin/cupsd" pid=26540 comm="apparmor_parser"
[17169.492953] audit: type=1400 audit(1421413284.207:1702): apparmor="STATUS" operation="profile_replace" profile="unconfined" name="third_party" pid=26540 comm="apparmor_parser"
[17169.496523] init: cups main process (26541) terminated with status 1
[17169.496532] init: cups main process ended, respawning

I've tried

sudo apt-get purge cups
sudo apt-get install cups --install-suggests

but still no change.

I've filed a bug about this at https://bugs.launchpad.net/ubuntu/+source/cups/+bug/1407958 but is there anything obvious I've missed/should have checked?

Answer 1

After a bit of searching and playing around, thanks to @Benjamin's comment above, I finally found that there is a default configuration file which should be installed in /usr/share/cups/cupsd.conf.default.

I ran

sudo cp /usr/share/cups/cupsd.conf.default /etc/cups/cupsd.conf
sudo service cups restart

and since then it worked!

I still have no idea how the file got lost in the first place though.

Answer 2

I ran:

sudo apt-get purge cups
sudo apt-get install cups --install-suggests

and then I checked that the configuration was correct. I still got a cups error trying to access a network HP printer, and I had to reinstall the printer, and then I got it to work.