LightBurn "Port failed to open - already in use?" on Ubuntu 24.02

I spent several hours and found an indirect answer to my particular setup:

  • Repurposed a Microsoft Surface Laptop 3 with Ubuntu 24.02
  • Linux LightBurn 1.6.00
  • LaserPecker 4 with firmware 6.5.5

Waiting for connection…
Port failed to open - already in use?
Waiting for connection…
Port failed to open - already in use?


"There is probably no real usage of the line, but a permission issue. quick and dirty way to test for me was to execute:

ls -la /dev/ttyUSB0
sudo chmod 666 /dev/ttyUSB0

I think that was the actual fix, but before that I also removed CH341 and installed CH340 drivers and added my username to the ‘dialout’ group. I would link to those instructions, but “new users can only insert two links”.

As soon as I executed “sudo chmod 666 /dev/ttyUSB0”, the LaserPecker 4 fired up and i didn’t have to select anything special in LightBurn (I had already followed the setup instructions provided by LaserPecker).

Commonly these end up with the dialup group… Usually if you add that group to your groups, it will have the proper access… Sometimes you have to set the protection anyway…

This is mine from Ubuntu

crw-rw---- 1 root dialout 4, 64 May 11 07:48 /dev/ttyS0


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Remember - if you add a group to a user that’s logged in (i.e. you), you need to logout and back in for the new groups to appear.

You can check with groups you have access to in your current session with the command groups in the command line.