printing via serial to usb cable
Rashkae
ubuntu at tigershaunt.com
Wed Jan 28 17:21:38 UTC 2009
Wade Smart wrote:
> Rashkae wrote:
>> Wade Smart wrote:
>>> 20090128 0906 GMT-5
>>>
>>> I recently posted about my parallel to usb cable causing lots of
>>> problems on my system - and since I received no help there I decided to
>>> try something else.
>>>
>>> I borrowed a serial to usb cable. I was able to print a test page by:
>>> sudo echo "Printer Test" > /dev/ttyUSB0
>>>
>>> but I havent been able to print any other way.
>>>
>>> In cups I changed the uri to usb://dev/ttyUSB0 and then I ran the
>>> configure script but nothing changed.
>>>
>>> What else can I try?
>>>
>>> Wade
>>>
>> Try a serial URI
>>
>> ex: serial:/dev/ttyUSB0?baud=11500
>>
>> Also note: I think (without being absolutely certain) that you only use
>> 1 / when you refer to a file (or a device note) directly on your system,
>> use // when your are specifying a network resource. I don't know if
>> that matters or if CUPS is smart enough to figure that out on it's own.
>> ( // also seems to be used by USB printers that are named by their
>> model number rather than a device note, for examply, in my system, I
>> have usb://Samsung/ML-1740 compared to parallel:/dev/lp0)
>>
>
> 20090128 1007 GMT-5
>
> Okay... LaserJet4050 (Default Printer) "Unable to open device file
> "/dev/ttyUSB0": Permission denied"
>
> And in my logs:
> Jan 28 10:05:42 wadesmart kernel: [145933.655140]
> audit(1233158742.764:27): type=1503 operation="inode_permission"
> requested_mask="rw::" denied_mask="rw::" name="/dev/ttyUSB0" pid=28751
> profile="/usr/sbin/cupsd" namespace="default"
>
> Jan 28 10:05:43 wadesmart kernel: [145934.058182]
> audit(1233158743.168:28): type=1503 operation="inode_permission"
> requested_mask="::rw" denied_mask="::rw" name="/dev/tty" pid=28757
> profile="/usr/sbin/cupsd" namespace="default"
>
> Jan 28 10:06:26 wadesmart kernel: [145977.419281]
> audit(1233158786.616:29): type=1503 operation="inode_permission"
> requested_mask="rw::" denied_mask="rw::" name="/dev/ttyUSB0" pid=28801
> profile="/usr/sbin/cupsd" namespace="default"
>
> Jan 28 10:06:27 wadesmart kernel: [145977.820661]
> audit(1233158787.020:30): type=1503 operation="inode_permission"
> requested_mask="::rw" denied_mask="::rw" name="/dev/tty" pid=28808
> profile="/usr/sbin/cupsd" namespace="default"
>
> Wade
By default, Ubuntu gives read/write permission to User root and group lp
for printer devices.
Unfortunately, the device scripts probably don't realize your serial
device is supposed to be a printer device, and therefore lp group (which
cups user is probably using) doesn't have write permission.
You can test with the following:
first, make sure that the device is not a symlink to somewhere else.
ls -lh /dev/ttyUSB0
then, assuming we have the correct device file:
sudo chown root:lp /dev/ttyUSB0
sudo chmod 660 /dev/ttyUSB0
Then try printing again and let us know if it works. Unfortunately,
making these changes permanent requires a bit more voodoo.. Hopefully
someone can step in, else I'll research it further.
PS: Karl has a well known habit on this list to jump in to topics way
over his head to either hilarious or catastrophic result. I suggest
liberal use of salt grains.
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