how_to_create_a_udev_rules.md

How to create a udev rules

• Introduction
• Create The New UDEV Rules
  • Create new udev file
  • Query serial port number through udevadm
  • Create UDEV Permission Rule For tty Devices
• Restart The UDEV Service

Introduction

The serial port is used under Linux. The serial port number will change with the insertion order of multiple serial ports. This problem can be solved by setting the serial port alias.

Create The New UDEV Rules

Create a new ydlidar_ports.rules file and write the corresponding serial port rules to the file.

Create new udev file

sudo gedit /etc/udev/rules.d/ydlidar_ports.rules

or

sudo vim /etc/udev/rules.d/ydlidar_ports.rules

Query serial port number through udevadm

udevadm info -a -n /dev/ttyUSB0 | grep KERNELS

result as follows:

udevadm info -a -n /dev/ttyUSB1 | grep KERNELS

result as follows:

Create UDEV Permission Rule For tty Devices

Write the first KERNELS queried above into the new ydlidar_ports.rules file. Add these two following rules in it.

SUBSYSTEM=="tty", KERNELS=="1-1:1.0", SYMLINK+="ydlidar", MODE="0666", GROUP:="dialout"
SUBSYSTEM=="tty", KERNELS=="1-2:1.0", SYMLINK+="ydlidar1", MODE="0666", GROUP:="dialout"

Restart The UDEV Service

Save the file and close it. Then as root, tell systemd-udevd to reload the rules files (this also reloads other databases such as the kernel module index), by running.

sudo udevadm control --reload

and

sudo service udev reload
sudo service udev restart

Note: If it doesn't work, plug and unplug the USB or restart the computer

You can query the corresponding results with the following command

ls -l /dev/ydlidar*

lrwxrwxrwx 1 root dialout 7 Feb 17 13:27 /dev/ydlidar -> ttyUSB0
lrwxrwxrwx 1 root dialout 7 Feb 17 13:27 /dev/ydlidar1 -> ttyUSB1