How do I allow non-root access to /ttyUSB0 on 12.04?

Question

Since I updated from 10.04 to 12.04, I am unable to access the device connected in /ttyUSB0 if I don't have root access. To be more specific, I use a usb-to-serial com port converter to access and configure Cisco equipment with a software called Putty. It happens that, since I upgraded to 12.04, Putty only sees the connected device when I run it as gksudo putty. If not, it says "unable to connect to port /ttyUSB0". I have managed to change the permissions via chmod 666, and it works, but if I disconnect the usb and reconnect, it goes back to root only. How do I permanently allow non-root access? I have a clue it might be via udev rules, but I have no idea how to do it.

obs. Manufacturer and drivers "PROLIFIC"

Answer 1

It's possible this is related to modemmanager, as detailed here.

I removed that (sudo apt-get remove modemmanager) and it fixed my problem.

You still need to be in the dialout group though.

Answer 2

The device is most likely attached to user group dialout. Just add your user to the dialout group so you have appropriate permissions on the device.

sudo usermod -a -G dialout $USER

(You may need to logout and back in for the new group to take effect.)

No need to mess around with permissions or udev rules.

Answer 3

sudo adduser <the user you want to add> dialout
sudo reboot

Mentioned by "Try now" worked for me. Check that You have dialout as group for ttyUSB0:

ls -l /dev/ttyUSB0

in my case the output is:

crw-rw---T 1 root dialout 188, 0 Feb 12 12:01 /dev/ttyUSB0

Answer 4

This worked for me. Just press Ctrl+Alt+T on your keyboard to open Terminal. When it opens, run the command below.

sudo adduser <the user you want to add> dialout
sudo reboot
id -Gn

Try now.

Answer 5

As reported by Rinzwind, start by typing:

sudo usermod -a -G dialout $USER

But that is only part of the solution, as then you must reboot the system:

sudo reboot

Answer 6

I tried both

sudo usermod -a -G dialout $USER #(worked perfectly)

And sudo chmod 666 /dev/ttyUSB0 (worked but had to type the command again)

I also removed the mode manager but did not really help. Therefore, the best command that worked for me was

sudo usermod -a -G dialout $USER

Answer 7

I had this problem with /dev/ttyS0 in Mint Rosa. Adding the user to the dialout group is required but in my case the device access was restricted and I had to expand it to give r/w access to group level also.

Answer 8

navigate to /etc/ folder and edit the group file add your username like this dialout:x:20:USER

worked perfect for me :)