Permission Denied: Solving HID Access Issues Without Sudo in Ubuntu 24.04

A common hurdle for developers and hardware enthusiasts on Ubuntu 24.04 LTS is the "Sudo-only" trap for Human Interface Devices (HID). You may have an external controller, a custom mechanical keyboard, or an SDR dongle that functions perfectly when run as sudo, but fails to initialize or appears "invisible" to user-level applications. Even after adding a standard udev rule, the system may still deny access. This is often due to the heightened security posture in Noble Numbat, including how systemd-logind manages device seats and the specific groups required for raw HID communication. This guide details how to correctly bridge the gap between kernel-level hardware detection and user-space permissions.

Table of Content

• Purpose of User-Space HID Access
• Common Scenarios for HID Permissions
• Step-by-Step: Fixing the Udev Bypass
• Best Results: ACL vs. Group Methods
• FAQ
• Disclaimer

Purpose

The primary purpose of this tutorial is to establish Non-Privileged Access to hardware. Running applications that interact with HID devices (like VIA for keyboards, OpenRGB, or custom Python scripts using hidapi) as root is a significant security risk. By correctly configuring the udev subsystem, we instruct the Linux kernel to change the ownership or permissions of a specific device node (typically found in /dev/hidraw) the moment it is plugged in, allowing your standard user account to read and write data safely.

Use Case

This fix is essential for users dealing with:

• Custom Peripherals: Mechanical keyboards that need firmware updates via web-based tools (WebHID).
• Gaming Gear: Controlling RGB lighting or button mapping on high-end mice and controllers.
• Development: Writing software in C++ or Python that communicates with USB devices using raw reports.
• Legacy Hardware: Specialized HID equipment that lacks official Linux drivers and requires direct communication.

Step-by-Step

1. Identify the Vendor and Product ID

You must tell Ubuntu exactly which device to apply the rule to.

• Plug in your device and run: lsusb.
• Find your device in the list. It will look like: Bus 001 Device 004: ID 1234:abcd Example HID Device.
• In this example, 1234 is the Vendor ID (idVendor) and abcd is the Product ID (idProduct).

2. Create the Udev Rule File

Udev rules must be stored in a specific directory with a high priority number.

1. Open a terminal and create a new rule file: sudo nano /etc/udev/rules.d/99-hid-device.rules.
2. Paste the following line, replacing the IDs with your own:
   KERNEL=="hidraw", SUBSYSTEM=="hidraw", ATTRS{idVendor}=="1234", ATTRS{idProduct}=="abcd", MODE="0666", TAG+="uaccess"
3. The MODE="0666" allows everyone to read/write, while TAG+="uaccess" delegates management to the current active seat (recommended for Ubuntu 24.04).

3. Reload Udev Rules

The system needs to be told to look at the new file.

• Run: sudo udevadm control --reload-rules
• Run: sudo udevadm trigger
Crucial Step: Unplug the HID device and plug it back in for the changes to take effect.

4. Verify Device Permissions

Check if the rule worked by looking at the device node:

• Run: ls -l /dev/hidraw
• You should see crw-rw-rw- (the 666 mode) or see that your username has been granted access via Access Control Lists (ACLs) if using uaccess.

Best Results

Method	Security Level	Stability
MODE="0666"	Low (All users can access)	High (Works everywhere)
GROUP="plugdev"	Medium (Requires group membership)	Moderate (Can be inconsistent)
TAG+="uaccess"	High (Only logged-in user)	Very High (Standard for Modern GNOME)

FAQ

Why is 'sudo' still required after reboot?

Ensure your rule file ends in .rules and doesn't have a hidden extension. Also, verify that no other rule with a higher number (like 100-something) is overriding your permissions. Using TAG+="uaccess" is the most modern way to solve this in Ubuntu 24.04.

What if my device has multiple 'hidraw' nodes?

The udev rule using KERNEL=="hidraw" will apply to all of them. This is usually desired, as different nodes represent different functionalities of the same physical USB device (e.g., keyboard keys vs. media controls).

Do I need to be in the 'dialout' or 'plugdev' group?

In older versions of Ubuntu, yes. In 24.04, if you use the uaccess tag in your udev rule, systemd-logind handles the permissions dynamically for whoever is physically at the computer, making extra group memberships unnecessary.

Disclaimer

Providing 0666 permissions to device nodes allows any software (including malicious scripts) to monitor your HID inputs or send commands to the hardware. Use specific Vendor and Product IDs rather than generic wildcards whenever possible. This guide reflects the security architecture of Ubuntu 24.04 LTS as of March 2026.

Tags: Ubuntu2404, HID, UdevRules, LinuxPermissions