Arduino program only works when run as root

Question

Uploading simple sketches seems to work when I run the Arduino program as root (sudo). I would like to run it as a regular user. Has anyone faced the same problem before and fixed it?

Here is what I obtained from lsusb:

$ lsusb
Bus 002 Device 022: ID 2341:0043 Arduino SA Uno R3 (CDC ACM)

And the Arduino program identifies it as /dev/ttyACM0. Here are its permissions:

$ ls -l /dev/ttyACM0 
crw-rw---T 1 root dialout 166, 0 Mar 14 22:03 /dev/ttyACM0

Here is the output from id

groups=1000(abhiram),20(dialout),24(cdrom),25(floppy),29(audio),
30(dip),44(video),46(plugdev),105(scanner),110(bluetooth),112(netdev)

When I upload an sketch from the examples, as a regular user, I encounter this error:

avrdude:stk500_recv(): programmer not responding

Any suggestions are welcome.

• alexan_e: See if this helps, section "SET THE PERMISSION"
• jippie: And +1 for not accepting the situation to run the IDE as root, but trying to figure out how to properly solve the issue.
• jippie: What is the exact error you get when you try to run the IDE under a non-privileged user? You may need to enable verbose output in the Preferences menu.
• jippie: Ensure you are connecting to the correct device, by unplugging, then wait for a few seconds, then replug, then check the output of dmesg for the device file that is registered.
• feverDream: Checked that, the device is discovered properly as /dev/ttyACM0: USB ACM device. So, it doesn't seem like problem to me. On the other hand, the logs from compiling and uploading( had to enable them in Preferences), seem promising. I just can't seem to copy them from the arduino program :(. (may be they are writing to a file somewhere?)

Answer 1

The easiest solution is to add yourself to the dialout group.

First make a note of the output from id. Save it in file (not in /tmp as that gets cleaned out on a reboot). If you look at the output, you'll notice that your user is signed up for several groups and those groups represent extra privileges on the system. By default your Arduino is assigned to the group dialout because it registers as a serial interface and in the old days these were often used to ... dial out, using a modem.

To add yourself to the dialout group, issue the following command:

sudo usermod -a -G dialout $USER

Don't forget the -a flag (for appending groups rather than replacing) or you will have entirely different problems. This is the reason for making a copy of the id output to a file, so in case you do mess up at least you know what your user was configured like before.

Then log out and log in and it should work from that point.

Optionally you can double check the output for id against the output you saved before.

• feverDream: thanks @jippie, for the thoughtful answer. I have added myself to the dialout group, but the problem still seems to persist. I have modified my question with the output from the id command.
• jippie: My impression from your update is that the exact cause of the problem has shifted to the next issue. You are on your way to solve it. What happens when you cat /dev/ttyACM0? Does it throw an error?
• feverDream: No, the device file seems to empty, when I cat it.
• jippie: Empty is OK, as long as you don't get an error message.

Answer 2

The oft-repeated advice to "just do sudo usermod -aG dialout <username> never worked for me, and I finally figured out why. On my machine, /dev/ttyUSB0 is of the group serial and not dialout, so adding my username to dialout did nothing.

# ls -l
# crw-rw---- 1 root serial 188, 0 Mar 31 20:52 /dev/ttyUSB0
 ^^^^^^ (group-name)

Finally: sudo usermod -aG <group-name> <username> fixed it for me.

Embarrassingly, this is also explicitly mentioned here under "SET THE PERMISSION". Sigh.

• Chris Stratton: Yes, it's worth checking the actual owning group. Also the device file can be either a ttyUSB# or a ttyACM# (or theoretically anything) depending on the board type, kernel driver, and ultimately configuration of udev or whatever creates the nodes.
• Roberto Tyley: It's also mentioned at arduino.cc/en/Guide/Linux#toc6

Answer 3

This happens to me. In my case, I had upgraded the version of arduino and seems the preferences file was causing the problem. Just delete ~/.arduino/preferences.txt file (with Arduino IDE closed).

Steps:

1. Close Arduino IDE

2. execute this:

   rm ~/.arduino/preferences.txt

3. Launch Arduino IDE

This worked for me, hope it works for someone else. I am using Linux Mint 17 and I upgraded from Arduino 1.05 to Arduino 1.06 by extracting the Arduino IDE, I am not using the one in the repo. (Of course, after adding your user to the corresponding group as mentioned by others, but if that wont help you try this)

• Chris Stratton: Possibly related to this, one side effect of running tools as root is that you can end up leaving behind temporary, config, or project files which your ordinay account cannot modify or clean up.