Cannot open /dev/ttyUSB0: Permission denied

[Navis-Raven]

I had an issue , while trying to do flash
Cannot open /dev/ttyUSB0: Permission denied

https://bugs.launchpad.net/ubuntu/+source/gtkterm/+bug/949597

I palliated to this problem with the command " sudo chmod -R 777 /dev/ttyUSB0 " each time I wanted to flash.

Do you know more about these bugs ? This maybe due to an ubuntu bug (Ubuntu 16 LTS) but I don't know

[ConstantJoe]

I'm not a dev on this project, just a user so if anyone else wants to jump in please do:

This is not an issue with the esp8266, and its not actually a bug at all, its just part of Linux. Its best practice to not change permissions in /dev unless as a last resort. What you want to do instead is to add yourself to the group which would give you permission to access the tty ports.

To see the groups you are in simply type:

groups

To see all available groups type:

compgen -g

Most of them are self-explanatory, in this case you want to add yourself to either the tty group, or dialout, which you would do by:

sudo usermod -a -G tty yourname

Then your user should have access to tty without use of sudo.

[stefanofiorentino]

After the sudo usermod -a -G tty yourname you have to logout/login to get group addition happens.

[kbhuinfo]

I had to add my user to group "dialout" too (ubuntu). Logout/login required.

[bumbalu]

Thank you people, it helped me to get access to my 3d printer from Klipper on Raspberry Pi!

[abstract17]

PROPER LOGOUT IS REQUIRED

[Taudris]

Can this issue be added to the install documentation? Or even better, is there a way to automate handling it?

[shamo1]

this is actually a permission problem u have to allow your Arduino IDE to access the specified port just simply type following commands in your terminal

sudo su
//type your password
cd /
cd dev
chown username ttyUSB0

[fr3kz]

thank you shamo1, it helped me

[Vince55]

thanks shamo1, that worked for me too!

[tdgi]

I add myself to dialout group and it works:
sudo usermod -a -G dialout your_user_name

[BlagoD]

I had to add my user to group "dialout" too (ubuntu). Logout/login required.

Indeed, without being member of the "dialout" group, the access to the ttyUSB is not granted.
Thanks for pointing it out!

[m-atoms]

note for future users who are curious about this

Problem
Cannot open /dev/ttyUSB0: Permission denied error is caused by the user not having access to the serial ports as other commenters have mentioned. More specifically, the user is not in the dialout group.

Solution
sudo usermod -a -G dialout $USER

For anyone who likes knowing what they're running before they run it:
usermod - modify a user account
-a - add the user to supplementary groups
-G - a list of supplementary groups (man page says to use -a only with -G)
dialout - group that controls access to serial ports (and other hardware too)
$USER - Bash variable containing current username (not a builtin, usually automatically set env variable)

bonus notes: This is the 'linux way' to solve the problem. Adding the user to the group with permission to use the device is much safer than changing the permissions of the device itself. And as others have mentioned, make sure you log out for the changes to take effect.