udev Notes
Table of Contents
Resources
Getting Info About a Device
- To see info about
/dev/foorunudevadm info /dev/foo
Rules
Naming Rules
- They must have the file extension
.rules - The files must be prefixed with a two digit number
- The number specifies the order that the rule will be applied
- Typically user rules are between 61 and less than 99
Locations
- udev rules reside in the
/etc/udev/rules.dfolder - Packages include udev rules and are in
/usr/lib/udev/rules.d - The rules inside
/etctake precedence over the/usr/librules
Example USB TTY Rule
- This example rule should set a USB TTY device that matches the vendor ID and product ID to have the permissions
0666or read and write for all users - This rule could be named
61-usb-serial-read-write.rules
SUBSYSTEM=="tty", ATTRS{idVendor}=="dead", ATTRS{idProduct}=="beef", MODE="0666"
Testing Rules
- If you want to test newly created rules before applying them you can use
udevadm test - You will need to use the
/devices/path of the device to test the rules - For example,
sudo udevadm test /devices/pci0000:00/0000:00:14.0/usb3/3-6/3-6:1.0/ttyUSB0/tty/ttyUSB0
Reloading Rules
- To reload the current rules run
sudo udevadm control --reload-rulesthensudo udevadm trigger