Preview build — page text is a draft awaiting human review. Code badges come from real compiles. The flasher is real but not yet hardware-tested; the Playground is still a preview.
Get Started
Upload error · Linux

Fix “[Errno 13] Permission denied: '/dev/ttyUSB0'” on Linux

Your Linux user isn't allowed to open the serial port. Join the dialout (or uucp) group, log out and back in — and give Snap/Flatpak IDEs serial access.

ESP32ESP8266Arduino UnoArduino NanoRaspberry Pi PicoUpdated 3 Nov 2026

Community draft — report a mistake

What you see

OutputOutput
esptool.py v4.8.1
Serial port /dev/ttyUSB0

A fatal error occurred: Could not open /dev/ttyUSB0, the port is busy or doesn't exist.
([Errno 13] could not open port /dev/ttyUSB0: [Errno 13] Permission denied: '/dev/ttyUSB0')

Hint: Try to add user into dialout or uucp group.

Failed uploading: uploading error: exit status 2

On Linux, serial ports are files under /dev owned by a group your user is not in by default. esptool, avrdude and Thonny all fail the same way: they find the port but cannot open it.

Join the group, log out and back in, and the error is gone for good. With the Snap or Flatpak version of the IDE there is one more step, because those sandboxes block USB devices until you allow them.

Quick fix — try in order

  1. 1

    Add yourself to the serial group

    Ubuntu, Debian, Mint, Pop!_OS, Fedora: sudo usermod -aG dialout $USER. Arch, Manjaro: sudo usermod -aG uucp $USER. Check which group owns the port with ls -l /dev/ttyUSB0.

  2. 2

    Log out and back in (or reboot)

    Group changes only apply to new login sessions. Run groups afterwards — dialout must be in the list.

  3. 3

    Snap Arduino IDE: connect the serial plug

    The Snap package is sandboxed. Run sudo snap connect arduino:raw-usb (and arduino:serial-port if listed by snap connections arduino), or use the AppImage from arduino.cc instead.

  4. 4

    Flatpak IDE: same idea

    Flatpak builds need device access: flatpak override --user --device=all cc.arduino.IDE2, then restart the IDE.

  5. 5

    Don't fix it with sudo or chmod 666

    Running the IDE as root creates root-owned files in your sketchbook, and chmod resets at every replug. The group method is permanent and safe.

Why it happens

Why does Linux block it?

Serial devices are owned by root and the dialout group (uucp on Arch). Normal users outside that group can't open them.

avrdude shows a different line

For an Uno it reads avrdude: ser_open(): can't open device "/dev/ttyACM0": Permission denied. Same cause, same fix — genuine Unos appear as ttyACM0, CH340 clones as ttyUSB0.

No /dev/ttyUSB0 at all?

That's a different problem — on Ubuntu 22.04 and later the brltty package often grabs CH340 boards. See CH340 disconnected by brltty.

Board-specific notes

Raspberry Pi Pico: MicroPython and Arduino-Pico appear as /dev/ttyACM0. The same dialout fix applies.

↑↓ to move · Enter to open