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Since i updated from 10.04 to 12.04, i am unable to acces the device connected in /ttyUSB0 if i dont have root access. To be more specific, i use a usb-to-serial com port converter to acces 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 IDEIA how to do it.

obs. Manufacturer and drivers "PROLIFIC"

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5 Answers 5

up vote 1 down vote accepted

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.

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1  
What if I can't remove modemmanager? I have a friend that has a 3G modem, and it seems he can't remove modemmanager because of that. How can he access /ttyUSB0 on 12.04 without root, but without removing modemmanager? –  Leonardo Montenegro Jul 19 '13 at 12:22
    
You can try by stopping it? sudo stop modemmanager It worked for me. –  Aleks Aug 12 at 9:19

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

No need to mess around with permissions or udev rules.

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no success... still no acces to ttyUSB0 without root... any other ideas??? –  yurividal May 11 '12 at 16:16
    
I sign in to upvote. The cleanest solution. –  0x5f3759df Apr 10 '13 at 10:15

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.

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

worked perfect for me :)

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