Running Commands Without a Password Using Sudoers in Linux

Introduction#

Sometimes you write a script and have to enter a password every time—annoying, right? 😅 In this article, I'll address the sudoers passwordless command execution issue in a simple, friendly tone; I'll go step-by-step to show the source of the error and its secure solutions.

Source of the Problem#

In modern desktop environments like Wayland, xset may not work; instead, you need to write to the /sys/class/leds/inputX::scrolllock/brightness file to change keyboard lights. Writing to this file requires root privileges¹. If you used sudo tee in your script, the system might constantly ask for a password. The typical reminder for this is:

sudo: a password is required

Often, the reason is an incorrect or missing permission definition in the sudoers file.

Why is a Correct Permission Definition Important?#

• If you don't specify the full path of the program in the sudoers line, the system can't match the permissions.
• If the arguments given to the command do not match the permission definition, the operation will still ask for a password.
• There might be a syntax error in /etc/sudoers or /etc/sudoers.d/—which can lead to unexpected behavior.

Solution: Step-by-Step#

1. Use the Full Path of the Program#

Writing the full path of the command in the sudoers file is the most basic rule. For example, for tee:

friday13 ALL=(ALL) NOPASSWD: /usr/bin/tee

This line grants permission to run the /usr/bin/tee command with all arguments without a password. ✅

2. Use an Alias for Multiple Commands#

If you want to grant permission for multiple tools, creating a group is more organized:

Cmnd_Alias MYTOOLS = /usr/bin/tee, /usr/bin/pacman, /usr/bin/aurman
friday13 ALL=(ALL) NOPASSWD: MYTOOLS

3. Keep Changes Under /etc/sudoers.d/#

Instead of directly editing the main sudoers file, create a separate file:

sudo visudo -f /etc/sudoers.d/10_mytools

Example file content:

Cmnd_Alias MYTOOLS = /usr/bin/tee, /usr/bin/pacman, /usr/bin/aurman
friday13 ALL=(ALL) NOPASSWD: MYTOOLS

This method both maintains order and simplifies management.

4. Testing Methods#

To verify the changes, apply these steps:

sudo -k  # Clear the sudo cache
sudo -n /usr/bin/tee /sys/class/leds/input4::scrolllock/brightness <<< 1
sudo -l  # List the user's sudo permissions

The sudo -n command attempts to run without asking for a password; if it doesn't give an error, your setting is working correctly. ✅

Common Pitfalls and Things to Watch Out For#

Summary#

• It is mandatory to specify the full path in sudoers.
• Group permissions using Cmnd_Alias for easier management.
• Keep changes in /etc/sudoers.d/ and edit with visudo.
• Verify by testing with sudo -n and sudo -l.

Useful Commands#

sudo visudo -f /etc/sudoers.d/10_mytools
sudo -k
sudo -n /usr/bin/tee /sys/class/leds/input4::scrolllock/brightness <<< 1
sudo -l

Resources#

ArchWiki: Sudo - Root access man sudoers

Conclusion#

With these steps, you can solve the sudoers passwordless command execution problem securely and permanently. When you try it, write the result or which commands you allowed in the comments—let's build more secure settings together! 🎉