USB – How to Allow Non-Root Access to /ttyUSB0

rootusb

Since I updated from Ubuntu 10.04 (Lucid Lynx) to Ubuntu 12.04 (Precise Pangolin), 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 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 device 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 are "PROLIFIC"

Best Answer

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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Ubuntu – Send raw data to USB parallel port after upgrading to 11.10

The /dev/usb/lpX device files you are looking for are provided by the usblp driver. It seems in Ubuntu 11.10 though, that this driver has been blacklisted. See the /etc/modprobe.d/blacklist-cups-usblp.conf file:

# cups talks to the raw USB devices, so we need to blacklist usblp to avoid
# grabbing them
blacklist usblp

If you want to send data directly to the device still, you can temporarily load the driver with modprobe usblp (the blacklist only prevents the driver from being automatically loaded). Once you are done, you can unload it with modprobe -r usblp.

How to Allow Non-Default User to Use ttyUSB0

As you've noticed, the /dev/ttyUSB0 device has the group of dialout. All you need to do is add the second user to the dialout group:

sudo adduser second_user dialout

second_user will need to log out & log back in again for this to take effect.

Best Answer

Related Solutions

Ubuntu – Send raw data to USB parallel port after upgrading to 11.10

How to Allow Non-Default User to Use ttyUSB0

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