Hi Mark,
on some systems, especially those with systemd, there is another directory
where udev looks for rules files. Did you check in
/usr/lib/udev/rules.d
for a file that might set the permissions for those devices?
Regards
Jörn
Am Montag, 25. September 2023, 23:52:10 CEST schrieb Mark Rivers via Tech-
talk:
> Folks,
>
> I am seeing something I don't understand about USB device permissions on
> Linux. I have two Centos 9 systems, each connected to 3 USB devices from
> Measurement Computing.
>
> On the system called 13ide I needed to install a udev rules file in order to
> give these USB devices world write permission.
>
> This is part of the rules file:
>
> (base) [epics@13ide ~]$ more /etc/udev/rules.d/50-uldaq.rules
> SUBSYSTEM=="usb", ATTR{idVendor}=="09db", ATTR{idProduct}=="0076",
> GROUP="adm", MODE="0666" SUBSYSTEM=="usb", ATTR{idVendor}=="09db",
> ATTR{idProduct}=="007f", GROUP="adm", MODE="0666" SUBSYSTEM=="usb",
> ATTR{idVendor}=="09db", ATTR{idProduct}=="0085", GROUP="adm", MODE="0666"
> SUBSYSTEM=="usb", ATTR{idVendor}=="09db", ATTR{idProduct}=="0086",
> GROUP="adm", MODE="0666" SUBSYSTEM=="usb", ATTR{idVendor}=="09db",
> ATTR{idProduct}=="008a", GROUP="adm", MODE="0666"
>
> lsusb shows that the devices are on bus 002, devices 005, 007, and 008.
>
> (base) [epics@13ide ~]$ lsusb
> Bus 002 Device 009: ID 0557:2259 ATEN International Co., Ltd LCD Console
> V1.3.124 Bus 002 Device 006: ID 0557:2259 ATEN International Co., Ltd LCD
> Console V1.3.124 Bus 002 Device 004: ID 0557:8021 ATEN International Co.,
> Ltd Hub
> Bus 002 Device 008: ID 09db:013e Measurement Computing Corp. USB-1808X
> Bus 002 Device 007: ID 09db:009d Measurement Computing Corp. USB-3104
> Bus 002 Device 005: ID 09db:0127 Measurement Computing Corp. USB-CTR08
>
> This shows that those devices have permission 666 and are owned by the "adm"
> group.
>
> (base) [epics@13ide ~]$ ls -l /dev/bus/usb/002
> total 0
> crw-rw-r-- 1 root root 189, 128 Sep 19 11:45 001
> crw-rw-r-- 1 root root 189, 129 Sep 19 11:45 002
> crw-rw-r-- 1 root root 189, 130 Sep 19 11:45 003
> crw-rw-r-- 1 root root 189, 131 Sep 19 11:45 004
> crw-rw-rw- 1 root adm 189, 132 Sep 19 11:45 005
> crw-rw-r-- 1 root root 189, 133 Sep 19 11:45 006
> crw-rw-rw- 1 root adm 189, 134 Sep 19 11:45 007
> crw-rw-rw- 1 root adm 189, 135 Sep 19 11:45 008
> crw-rw-r-- 1 root root 189, 136 Sep 19 11:45 009
>
> This makes sense to me because permission 666 and group "adm" are in the
> 50-uldaq.rules file.
>
> However, I have another system which does not have a udev rules file in that
> location.
>
> [epics@13idc ~]$ ls -l /etc/udev/rules.d/
> total 0
>
> On that system the devices are on bus 001, devices 004, 005, and 006.
>
> [epics@13idc udev]$ lsusb
> Bus 002 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub
> Bus 001 Device 010: ID 1604:10c0 Tascam Dell Integrated Hub
> Bus 001 Device 009: ID 413c:a102 Dell Computer Corp. iDRAC Virtual NIC
> Bus 001 Device 007: ID 1604:10c0 Tascam Dell Integrated Hub
> Bus 001 Device 003: ID 1604:10c0 Tascam Dell Integrated Hub
> Bus 001 Device 006: ID 09db:013e Measurement Computing Corp. USB-1808X
> Bus 001 Device 005: ID 09db:009d Measurement Computing Corp. USB-3104
> Bus 001 Device 004: ID 09db:0127 Measurement Computing Corp. USB-CTR08
> Bus 001 Device 002: ID 0409:005a NEC Corp. HighSpeed Hub
> Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
>
> The following shows that these devices also have permissions 666 and are in
> the "adm" group.
>
> [epics@13idc udev]$ ls -l /dev/bus/usb/001
> total 0
> crw-rw-r-- 1 root root 189, 0 Sep 19 12:09 001
> crw-rw-r-- 1 root root 189, 1 Sep 19 12:09 002
> crw-rw-r-- 1 root root 189, 2 Sep 19 12:09 003
> crw-rw-rw- 1 root adm 189, 3 Sep 19 12:09 004
> crw-rw-rw- 1 root adm 189, 4 Sep 19 12:09 005
> crw-rw-rw- 1 root adm 189, 5 Sep 19 12:09 006
> crw-rw-r-- 1 root root 189, 6 Sep 19 12:09 007
> crw-rw-r-- 1 root root 189, 8 Sep 19 12:09 009
> crw-rw-r-- 1 root root 189, 9 Sep 19 12:09 010
>
> I don't understand this, since there is no rules file. How did it know to
> assign these permissions and group? Is there another mechanism by which
> USB devices get permissions assigned?
>
> Thanks,
> Mark
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