In Arduino IDE the serial port is greyed out and COM 1 i shown in the window There is no way to communicate trough serial connection. Dont know if this is a Arduino Bugg or a bugg in Bionic Beaver. The application worked in 17.10 Artfull.

This bugg is reported and a fix is awaiting an upload in debian

May 9:

Fixed the NullPointerException with Java 10 caused by the null java.ext.dirs system property (Closes: #896929)

Its not a Arduino only problem but affect serial connections in general.

Tested Pronterface and there is no serial connection to 3D printer.

  • 2
    Just some added info: This is a known issue with Ubuntu 18.04 as Arduino IDE throws an Exception when loading the Serial Driver. Specifically: java.lang.NullPointerException thrown while loading gnu.io.RXTXCommDriver
    – user693336
    May 10, 2018 at 1:34
  • 1
    So it's a known problem. But there is no Known solutions (yet)?
    – bolean
    May 10, 2018 at 9:08
  • 1
    Possible duplicate of How to install latest Arduino IDE?
    – N0rbert
    May 10, 2018 at 17:54
  • This is actually a bug in librxtx-java and is fixed in Debian version 2.2pre2+dfsg1-2. Ubuntu has this since Cosmic. For Bionic you can download and install the Comic version by hand.
    – kleptog
    Jun 15, 2019 at 13:31

5 Answers 5


The serial communication/uploader problem was fixed for me by following the instructions for installing Oracle java 8 from this posting:


on a newly installed Ubuntu 18.04 LTS system. After installing Oracle java 8:

  • $ sudo add-apt-repository ppa:webupd8team/java
  • $ sudo apt update
  • $ sudo apt install oracle-java8-set-default

the Arduino IDE worked properly.

  • This workaround works for me. Serial port no longer greyed out.
    – bolean
    May 14, 2018 at 11:32
  • 1
    This is the best answer to solve the problem with arduino from repo, but the better outcome will be to install the latest version of arduino from arduino.cc, as the repo version is very old and missing many features (Library and Boards managers being significant omissions)
    – CharlieS
    Mar 8, 2019 at 21:28
  • 1
    My solution: install openjdk 8, then activate it via sudo update-alternatives --config java Jul 9, 2019 at 14:47
  • Thanks Stephan. I installed the openjdk-8-jdk package, which helped (with update-alternatives --config java) Oct 28, 2019 at 3:09

You should give your user permissions to write to serial port with

sudo usermod -a -G dialout $USER

Also see "How to install latest Arduino IDE?".

It seems that it is real bug, I also get on clean Ubuntu 18.04 LTS:

$ arduino
java.lang.NullPointerException thrown while loading gnu.io.RXTXCommDriver
java.lang.NullPointerException thrown while loading gnu.io.RXTXCommDriver

$ dpkg -S `which arduino`
arduino: /usr/bin/arduino

$ dpkg -l arduino | tail -n1
ii  arduino        2:1.0.5+dfsg2-4.1 all          AVR development board IDE and built-in librarie

so I reported bug 1770604 to launchpad with linked Debian Bugs:

  • I am a member of the dialout group
    – bolean
    May 10, 2018 at 9:02
  • I reported bug to launchpad.
    – N0rbert
    May 11, 2018 at 10:01

I was facing the same problem. I installed version Arduino IDE 1.9.0 beta and I no longer see that error.

  • Version 1.9.0 beta of what? Aug 5, 2018 at 3:27
  • 1
    @StephenRauch Arduino IDE version 1.9 beta.
    – karel
    Aug 5, 2018 at 4:11
  • Yes, Arduino IDE 1.9.0 beta. I worded a bit better my answer. Aug 5, 2018 at 14:56

Try it using,

sudo usermod -a -G dialout $USER

and, don't forget to change permission, example COM1 as ttyUSB0 :

ls -l /dev/tty*
sudo chmod a+rw /dev/ttyUSB0

Download the latest Arduino IDE from arduino.cc, extract the archive and make install.sh executable with chmod +x install.sh or through the Permissions tab of the file's properties. After this you can run sudo ./install.sh - from a terminal that has the extracted folder as its current path - to install the Arduino IDE. This should fix your problem.

Thanks to CharlieS for the suggestion by comment.

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