CUPS don't detect USB printer

artiom · 2009-02-08 18:17:57

I have 2 usb printers. An old hp deskjet and a new samsung ML-1640.The first works fine with hplip dirver. For the second I have installed the official Samsund driver via AUR. But CUPS don't see it. It is recognized by the kernel. I see /dev/usb/lp0 device created (root.lp rw-rw---) but still nothing in CUPS .

After searching similar problems on the net I have found a hint that changing permissions on the lp0 device can solve the problem. So chmod +rw lp0 and it WORKS.

But evidently after turn off, turn on of the printer lp0 will have its default permissions again. I tried to find the cause of the problem by comparing the system behavour with my printers. I found that it's identical. The devices are created with the same permissions.
I found also that changing the group of the device to nobody or owner to daemon have the same effect as chmod +rw (it works).

Anybody have an idea why this happen and how to fix it definitively ?

Last edited by artiom (2009-02-10 10:44:43)

artiom · 2009-02-10 10:08:50

Nobody here understands how CUPS works?

I see by ps -ef command a print task owned by daemon (and I suppose nobody group). I think that this print process try to access /dev/usb/lpx device. The same thing when I print to HP printer...

Last edited by artiom (2009-02-10 10:44:23)

artiom · 2009-02-10 10:13:37

I have added my udev rules so the lpx devices were created with daemon owner. Now it works, but I am not sure that it's a good idea.
And I still didn't understand why with the same permission CUPS prints on HP and not on SAMSUNG.

fwojciec · 2009-02-10 10:54:43

Have you tried using the instructions from linux printer database?
http://www.openprinting.org/show_printe … ng-ML-1640

artiom · 2009-02-10 10:58:04

Of cause I did. I can print when I change the permissions on the corresponding lp device.

kjon · 2009-02-10 13:06:55

Most printers of that class **do need** a slight udev tweak for making them work. Is not wrong to set a +rw on /dev/lp0, but if I were you, I would set a 0660@/dev/lp0 only if it matches your printer.

Maybe something like:

ACTION=="add", SUBSYSTEM=="usb", SYSFS{manofacturer}=="Samsung", MODE="0660", GROUP="lp"

Might help. Obviosly, you need to tweak that rule to your own needs, and **don't forget** to add yourself to the lp group.

Last edited by kjon (2009-02-10 13:08:20)

artiom · 2009-02-10 13:25:15

Ok, thanks. It's better than to treat all printers like this. But I rather apply daemon owner on my lp0. I find it better than MODE=0666 (cause 0660 will not work in my case). And I am already in lp group.

Why they do need this udev tweak? I didn't find anything special in its detection by udev and hal.

kjon · 2009-02-10 15:10:20

The udev rule is just for setting the correct permissions for the device. For instance, my multifunctional and my laser printer both needs a little of love to make them work (read, right permissions.)

artiom · 2009-02-10 15:15:55

I know, but what is incorrect in root.lp rw-rw--- ?

kjon · 2009-02-10 15:20:04

Nothing. Is up to the device. For me is pretty sane to have 0660 on a device, but my printer won't do its job unless it's set to 0666. So, in those cases it might be a driver issue. Nothing else comes into my mind.

Arch Linux

#1 2009-02-08 18:17:57

CUPS don't detect USB printer

#2 2009-02-10 10:08:50

Re: CUPS don't detect USB printer

#3 2009-02-10 10:13:37

Re: CUPS don't detect USB printer

#4 2009-02-10 10:54:43

Re: CUPS don't detect USB printer

#5 2009-02-10 10:58:04

Re: CUPS don't detect USB printer

#6 2009-02-10 13:06:55

Re: CUPS don't detect USB printer

#7 2009-02-10 13:25:15

Re: CUPS don't detect USB printer

#8 2009-02-10 15:10:20

Re: CUPS don't detect USB printer

#9 2009-02-10 15:15:55

Re: CUPS don't detect USB printer

#10 2009-02-10 15:20:04

Re: CUPS don't detect USB printer

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