getting-started/linux: instructive adding user to dialout group/add permissions to /dev/ttyACM0

[soypat]

Many new users to arduino if using tinygo will encounter this error https://askubuntu.com/questions/1056314/uploading-code-to-arduino-gives-me-the-error-avrdude-ser-open-cant-open-d.

I propose we add a link or small instructive on how to add your user to permitted users for the device dialout. I am available to create the PR.

From what I understand this is relevant info:

This error is usually encountered when flashing your first program, here's a typical error:

avrdude: ser_open(): can't open device "/dev/ttyACM0": Permission denied

The above error may be followed by ioctl errors too.

To fix this we must make sure our user is part of dialout group and that the correct permissions are set on the port.

First lets check the existence and permissions of the connected device (make sure your Arduino is connected):

 ls -l /dev/ttyACM0

In the author's case, this yields the output crw-rw---- 1 root dialout 166, 0 jul 13 12:45 /dev/ttyACM0. Notice the permissions are restrictive, we'd like all users to be able to read and write on this port.

To add read and write permissions on this port:

sudo chmod a+rw /dev/ttyACM0

The result of ls has now changed to crw-rw-rw-+ 1 root dialout 166, 0 jul 13 13:08 /dev/ttyACM0.

Let's also check if our user is in dialout group:

groups

Output: whoami adm cdrom sudo dip plugdev lpadmin lxd sambashare

To add our user to dialout we write:

sudo usermod -aG dialout $(whoami)

[aykevl]

If you want to add this to the FAQ, that would be appreciated.

However, regarding the solution: I don't think the chmod fix is ever a proper solution (it will probably stop working once you remove the device). Instead, adding yourself to the dialout group is the proper fix. We can perhaps make a list of Linux distributions and the group they use: perhaps other distributions use a different group name for /dev/ttyACM0 devices. So the solution would be: add yourself to the dialout group, log out and log in again.

[soypat]

Solved by #204