Ubuntu 20.04 Printer

[va7ru]

I was able to Duplicate the issue on 2 different systems and 1 VM all running Ubuntu 20.04. I am able to send a fax direct from the App. When I use the printer it fails. There is no system dialog that pops up and asks for Fax number etc.

[felixmartens]

Same problem here. Ubuntu 20.04, sending from yajhfc app manually works, but using the printer-driver does not open the sending dialog.

/var/log/cups/access_log (Just the part for yajhfc)
localhost - - [04/Jun/2020:12:32:46 +0200] "POST /printers/yajhfc HTTP/1.1" 200 223 Create-Job successful-ok localhost - - [04/Jun/2020:12:32:46 +0200] "POST /printers/yajhfc HTTP/1.1" 200 109626 Send-Document successful-ok
/var/log/cups/error_log
E [04/Jun/2020:12:32:46 +0200] [Job 229] cat error (RC=1): E [04/Jun/2020:12:32:47 +0200] [Job 229] Job held for 300 seconds since it could not be sent. E [04/Jun/2020:12:37:48 +0200] [Job 229] cat error (RC=1): E [04/Jun/2020:12:37:48 +0200] [Job 229] Job held for 300 seconds since it could not be sent.

[jwolz]

I have now installed Ubuntu 20.04 in a virtual machine and can confirm this problem.

The CUPS backend itself seems to work and the named pipe (/var/spool/yajhfc/printer-$USER) seems to work, too.
(The Linux fax printer works like this: YajHFC opens a named pipe called /var/spool/yajhfc/printer-$USER and the CUPS backend script basically just does a cat of the printed data to that pipe -- this is why you get the message "cat error (RC=1)")

However the backend seems to be unable to write to the named pipe.
I don't know why so far (probably some security related change in Ubuntu/systemd/CUPS). I will have to investigate this further when I have more time

[jwolz]

I finally found the reason for the problem:
It is indeed a new security feature, see https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1875225

Could you try if "sudo sysctl fs.protected_fifos=0" and then trying to print does fix this issue for you?

To make it a permanent workaround, you can create a file under /etc/sysctl.d as described in the linked bug report.

I will still have to find a way to make it work without changing this setting.

[felixmartens]

I confirm that this solves the problem. Great support!

[va7ru]

I too can confirm that this resolves the issue. Thanks So Much for your Great support.

[jwolz]

I think I have found a solution so that it works with the default setting of fs.protected_fifos=1 (at least it does in my VM).

Could you try if replacing /usr/lib/cups/backend/yajhfc with the file in the attached archive fixes the issue?

yajhfc-cups-backend.zip

[felixmartens]

It seems to work if the right permissions for the binary are set. Will test it on another system during the day.
Thanks for your quick support.

[jwolz]

Thanks for the feedback!

You can now also find new packages including the updated script at: https://download.yajhfc.de/betas/deb-repository/stable/deb-all/