Public bug reported:
When testing HPLIP I found out that CUPS backends can access my printer
only when they are running as root, when they are running as the special
user lp, as it is usually the case, they cannot access the printer.
So I tried to find out why and saw that the /dev/bus/usb/*/* device file
for the printer has group ownership "audio" and not "lp":
till@till-x1yoga:~/ubuntu/hplip/focal/debian/hplip-3.19.12+dfsg0$ ll
/dev/bus/usb/*/*
crw-rw-r-- 1 root root 189, 0 Feb 11 14:17 /dev/bus/usb/001/001
crw-rw-r-- 1 root root 189, 2 Feb 11 14:17 /dev/bus/usb/001/003
crw-rw-r-- 1 root root 189, 3 Feb 11 14:17 /dev/bus/usb/001/004
crw-rw-r-- 1 root plugdev 189, 4 Feb 14 12:23 /dev/bus/usb/001/005
crw-rw-r-- 1 root root 189, 5 Feb 11 14:17 /dev/bus/usb/001/006
crw-rw----+ 1 root audio 189, 62 Feb 14 12:37 /dev/bus/usb/001/063
crw-rw-r-- 1 root root 189, 128 Feb 11 14:17 /dev/bus/usb/002/001
crw-rw-r-- 1 root root 189, 130 Feb 13 09:38 /dev/bus/usb/002/003
till@till-x1yoga:~/ubuntu/hplip/focal/debian/hplip-3.19.12+dfsg0$
The printer is the device /dev/bus/usb/001/063:
till@till-x1yoga:~/ubuntu/hplip/focal/debian/hplip-3.19.12+dfsg0$ lsusb
Bus 002 Device 003: ID 0b95:1790 ASIX Electronics Corp. AX88179 Gigabit Ethernet
Bus 002 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub
Bus 001 Device 005: ID 138a:0097 Validity Sensors, Inc.
Bus 001 Device 004: ID 04f2:b5ce Chicony Electronics Co., Ltd Integrated Camera
Bus 001 Device 003: ID 8087:0a2b Intel Corp.
Bus 001 Device 006: ID 056a:50b7 Wacom Co., Ltd Pen and multitouch sensor
Bus 001 Device 063: ID 03f0:7a12 HP, Inc HP OfficeJet Pro 8730
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
till@till-x1yoga:~/ubuntu/hplip/focal/debian/hplip-3.19.12+dfsg0$
There must be a bug somewhere in the UDEV rules.
** Affects: pulseaudio (Ubuntu)
Importance: High
Status: New
** Affects: systemd (Ubuntu)
Importance: High
Status: New
** Affects: udev (Ubuntu)
Importance: High
Status: New
** Description changed:
When testing HPLIP I found out that CUPS backends can access my printer
only when they are running as root, when they are running as the special
user lp, as it is usually the case, they cannot access the printer.
So I tried to find out why and saw that the /dev/bus/usb/*/* device file
for the printer has group ownership "audio" and not "lp":
till@till-x1yoga:~/ubuntu/hplip/focal/debian/hplip-3.19.12+dfsg0$ ll
/dev/bus/usb/*/*
crw-rw-r-- 1 root root 189, 0 Feb 11 14:17 /dev/bus/usb/001/001
crw-rw-r-- 1 root root 189, 2 Feb 11 14:17 /dev/bus/usb/001/003
crw-rw-r-- 1 root root 189, 3 Feb 11 14:17 /dev/bus/usb/001/004
crw-rw-r-- 1 root plugdev 189, 4 Feb 14 12:23 /dev/bus/usb/001/005
crw-rw-r-- 1 root root 189, 5 Feb 11 14:17 /dev/bus/usb/001/006
crw-rw----+ 1 root audio 189, 62 Feb 14 12:37 /dev/bus/usb/001/063
crw-rw-r-- 1 root root 189, 128 Feb 11 14:17 /dev/bus/usb/002/001
crw-rw-r-- 1 root root 189, 130 Feb 13 09:38 /dev/bus/usb/002/003
+ till@till-x1yoga:~/ubuntu/hplip/focal/debian/hplip-3.19.12+dfsg0$
+
+ The printer is the device /dev/bus/usb/001/063:
+
+ till@till-x1yoga:~/ubuntu/hplip/focal/debian/hplip-3.19.12+dfsg0$ lsusb
+ Bus 002 Device 003: ID 0b95:1790 ASIX Electronics Corp. AX88179 Gigabit
Ethernet
+ Bus 002 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub
+ Bus 001 Device 005: ID 138a:0097 Validity Sensors, Inc.
+ Bus 001 Device 004: ID 04f2:b5ce Chicony Electronics Co., Ltd Integrated
Camera
+ Bus 001 Device 003: ID 8087:0a2b Intel Corp.
+ Bus 001 Device 006: ID 056a:50b7 Wacom Co., Ltd Pen and multitouch sensor
+ Bus 001 Device 063: ID 03f0:7a12 HP, Inc HP OfficeJet Pro 8730
+ Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
till@till-x1yoga:~/ubuntu/hplip/focal/debian/hplip-3.19.12+dfsg0$
There must be a bug somewhere in the UDEV rules.
** Also affects: systemd (Ubuntu)
Importance: Undecided
Status: New
** Changed in: systemd (Ubuntu)
Importance: Undecided => High
** Also affects: pulseaudio (Ubuntu)
Importance: Undecided
Status: New
** Changed in: pulseaudio (Ubuntu)
Importance: Undecided => High
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https://bugs.launchpad.net/bugs/1863239
Title:
/dev/bus/usb/*/* device file of HP multi-function printer assigned to
"audio" group
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