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I'm trying to install a device. I plug in the device which creates a ttyUSB0 file. When I open it in the program I need it for, it says the permission is denied. I type in terminal

sudo chmod 666 /dev/ttyUSB0

This resolved the problem but after restarting my computer I get the same problem and need to re-enter the same command to get permission. How do I fix this where I don't need to change the permission after every reboot?

2 Answers 2

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You can write udev rule to solve this. Google Keywords: udev usb permissions

You can take reference of this and this links.

Create a file /etc/udev/rules.d/51-my_usb_device (for instance). And put the following line:

SUBSYSTEMS=="usb", ATTRS{idVendor}=="10c4", ATTRS{idProduct}=="ea60", GROUP="users", MODE="0666"

Where HEX1 and HEX2 are replaced with the vendor and product id respectively. You can get vendor and product id from lsusb -vvv command.

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  • thanks a lot ill try this when i get home and post the results :)
    – Eugene G
    Nov 24, 2011 at 16:42
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in case you need to change (like me) ttyACM0 permissions, this are my settings:

KERNEL=="ttyACM0", MODE="0777"

It failed when I tried to specify the vendor and product id. I am not sure why.

If you want to restart udev without restarting the machine do this: (Redhat, EL6, Fedora)

udevadm control --reload-rules
start_udev

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