How to Configure Device File owner/group with udev rules?

Linux creates a device file under /dev for each hardware device when it is attached.
By default these files are owned by root and belong to a system group (for example root or dialout).
You can use udev rules to set a custom owner, group, and permissions so that non-root users can access the device.

Prerequisites

Before you begin:

• A Linux system with udev installed.
• Root or sudo access.
• Basic familiarity with the command line.

1. Identify the Device Attributes

First find the device’s attributes that udev can match:

udevadm info -a -n /dev/ttyUSB0

Look for lines under ATTR{idVendor} and ATTR{idProduct} or other unique identifiers.

2. Choose Owner, Group, and Mode

Decide which user and group should own the device file and what permission bits it needs. For example:

• Owner: your Linux username
• Group: plugdev (or create a custom group)
• Mode: 0660 (read and write for owner and group)

Make sure your user is in the chosen group:

sudo usermod -aG plugdev your_username

3. Create a udev Rule

Create a new rule file in /etc/udev/rules.d/. Use a high number so it loads late, for example 99-device-perms.rules:

sudo tee /etc/udev/rules.d/99-device-perms.rules <<EOF
# Set owner and group for USB device
SUBSYSTEM=="usb", ATTR{idVendor}=="abcd", ATTR{idProduct}=="1234", OWNER="your_username", GROUP="plugdev", MODE="0660"
EOF

Replace abcd and 1234 with your device’s vendor and product IDs, and your_username with your Linux user name.

4. Reload udev Rules and Trigger

Tell udev to reload its rules and apply them to existing devices:

sudo udevadm control --reload
sudo udevadm trigger

5. Verify the New Owner and Group

Check the device file’s permissions:

ls -l /dev/ttyUSB0

You should see your user and the plugdev group as owner and group.

Conclusion

You have now set a custom owner, group, and permissions for your device file using udev rules. This method ensures that every time the device is plugged in, udev applies the correct settings automatically.