[Pkg-cups-devel] Bug#506181: Various backends have the wrong permissions
Chanoch (Ken) Bloom
kbloom at gmail.com
Wed Nov 19 05:23:57 UTC 2008
After spending some time learning what the
rootbackends-worldreadable.dpatch in expermental does, and learning what
the code behind it does, I understand the problem.
I neither add a USB or parallel printer nor print to one in cups
1.3.8-1lenny2. Apparently the reason for this is that the relevant
backends are apparently not running with permissions to access the
relevant devices.
crw-rw---- 1 root lp 6, 0 2008-11-18 08:10 /dev/lp0
crw-rw---- 1 root dialout 4, 64 2008-11-18 08:09 /dev/ttyS0
crw-rw---- 1 root dialout 4, 65 2008-11-18 08:09 /dev/ttyS1
crw-rw---- 1 root dialout 4, 66 2008-11-18 08:09 /dev/ttyS2
crw-rw---- 1 root dialout 4, 67 2008-11-18 08:09 /dev/ttyS3
crw-rw---- 1 root lp 180, 0 2008-11-18 08:09 /dev/usb/lp0
These permissions are set in /etc/udev/rules.d/91-permissions.rules
CUPS default permissions for running filters (including the backends) is
to run in group lpadmin.
If I change the group that filters run in (adding the line "Group lp"
in /etc/cups/cupsd.conf) then I can make the usb and parallel backends
work. (But I can't make usb and parallel work at the same time as serial
because they require different groups to run)
If I change the permissions on the parallel, usb, and serial backends
from 755 to 700, then cups will run them as root (this is the behavior
that rootbackends-worldreadable.dpatch was dealing with, but not really
fixing in this instance) and they will all work.
--
Ken (Chanoch) Bloom. PhD candidate. Linguistic Cognition Laboratory.
Department of Computer Science. Illinois Institute of Technology.
http://www.iit.edu/~kbloom1/
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