user25578: I am running Ubuntu Mate 16.04 LTS, with an Arduino Uno R3 clone. I am having the dreaded serial port graying out problem, and have not found a solution for fixing it. Currently, The serial port will grey out sometimes, and sometimes it will be not grayed out, and I can see that I have selected ttyUSB0. Usually when it is not grayed out, uploading a sketch will not work, and I get the error like it is grayed out:

avrdude: ser_open(): can't open device "/dev/ttyUSB0": No such file or directory
  An error occurred while uploading the sketch

chmod a+rw /dev/ttyUSB0

doesn't solve the issue, with log out included
gpasswd -a aaron dialout

doesn't solve the issue, with log out included
I searched preferences.txt and serial.debug rate is set to 9600
I have tried entering preferences.txt and deleting all of the serial entries. They are recreated the same after deletion, and this doesn't solve anything.
I tried running as sudo, doesn't work.
I tried solving this originally on Arduino IDE 1.0, didn't work.
I have upgraded to Arduino IDE 1.6.10, still not working.
running lsusb in terminal yields this while Arduino is plugged in:
Bus 002 Device 002: ID 8087:0024 Intel Corp. Integrated Rate Matching Hub
Bus 002 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 001 Device 003: ID 0a5c:21e6 Broadcom Corp. BCM20702 Bluetooth 4.0 [ThinkPad]
Bus 001 Device 002: ID 8087:0024 Intel Corp. Integrated Rate Matching Hub
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 004 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub
Bus 003 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub

Checking var/log/syslog after plugging in Arduino:

kernel: [42043.787178] usb 3-2: new full-speed USB device number 109 using xhci_hcd
kernel: [42043.916241] usb 3-2: New USB device found, idVendor=1a86, idProduct=7523
kernel: [42043.916249] usb 3-2: New USB device strings: Mfr=0, Product=2, SerialNumber=0
kernel: [42043.916253] usb 3-2: Product: USB2.0-Serial
kernel: [42043.916964] ch341 3-2:1.0: ch341-uart converter detected
kernel: [42043.918199] usb 3-2: ch341-uart converter now attached to ttyUSB0
mtp-probe: checking bus 3, device 109: "/sys/devices/pci0000:00/0000:00:14.0
  /usb3/3-2"
mtp-probe: bus: 3, device: 109 was not an MTP device

Ran to add to dialout group, then logged out
sudo usermod -a -G dialout aaron

No solution.
So it looks like Arduino board is not being recognized. Not sure what to try next. It is important that I have uploaded sketches before, but am not sure if there is a pattern to when it does not work. It does not work 95% of the time.
Thanks for the help!

user30623: I have the same problem, 
I believe that the problem is related to the 4.x kernel, since I have already tried another distribution with the kernel mermo and the problem persists. Using a windows virtual machine as guest works, which excludes communications and hardware issues.

25578: <p>I am running Ubuntu Mate 16.04 LTS, with an Arduino Uno R3 clone. I am having the dreaded serial port graying out problem, and have not found a solution for fixing it. Currently, The serial port will grey out sometimes, and sometimes it will be not grayed out, and I can see that I have selected ttyUSB0. Usually when it is not grayed out, uploading a sketch will not work, and I get the error like it is grayed out:</p>

<blockquote>
  <p>avrdude: ser_open(): can't open device "/dev/ttyUSB0": No such file or directory
  An error occurred while uploading the sketch</p>
</blockquote>

<pre><code>chmod a+rw /dev/ttyUSB0
</code></pre>

<p>doesn't solve the issue, with log out included</p>

<pre><code>gpasswd -a aaron dialout
</code></pre>

<p>doesn't solve the issue, with log out included</p>

<p>I searched preferences.txt and serial.debug rate is set to 9600</p>

<p>I have tried entering preferences.txt and deleting all of the serial entries. They are recreated the same after deletion, and this doesn't solve anything.</p>

<p>I tried running as sudo, doesn't work.</p>

<p>I tried solving this originally on Arduino IDE 1.0, didn't work.</p>

<p>I have upgraded to Arduino IDE 1.6.10, still not working.</p>

<p>running lsusb in terminal yields this while Arduino is plugged in:</p>

<pre><code>Bus 002 Device 002: ID 8087:0024 Intel Corp. Integrated Rate Matching Hub
Bus 002 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 001 Device 003: ID 0a5c:21e6 Broadcom Corp. BCM20702 Bluetooth 4.0 [ThinkPad]
Bus 001 Device 002: ID 8087:0024 Intel Corp. Integrated Rate Matching Hub
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 004 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub
Bus 003 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
</code></pre>

<p>Checking var/log/syslog after plugging in Arduino:</p>

<blockquote>
  <p>kernel: [42043.787178] usb 3-2: new full-speed USB device number 109 using xhci_hcd</p>
  
  <p>kernel: [42043.916241] usb 3-2: New USB device found, idVendor=1a86, idProduct=7523</p>
  
  <p>kernel: [42043.916249] usb 3-2: New USB device strings: Mfr=0, Product=2, SerialNumber=0</p>
  
  <p>kernel: [42043.916253] usb 3-2: Product: USB2.0-Serial</p>
  
  <p>kernel: [42043.916964] ch341 3-2:1.0: ch341-uart converter detected</p>
  
  <p>kernel: [42043.918199] usb 3-2: ch341-uart converter now attached to ttyUSB0</p>
  
  <p>mtp-probe: checking bus 3, device 109: "/sys/devices/pci0000:00/0000:00:14.0
  /usb3/3-2"</p>
  
  <p>mtp-probe: bus: 3, device: 109 was not an MTP device</p>
</blockquote>

<p>Ran to add to dialout group, then logged out</p>

<pre><code>sudo usermod -a -G dialout aaron
</code></pre>

<p>No solution.
So it looks like Arduino board is not being recognized. Not sure what to try next. It is important that I have uploaded sketches before, but am not sure if there is a pattern to when it does not work. It does not work 95% of the time.</p>

<p>Thanks for the help!</p>
 30623: <p>I have the same problem, 
I believe that the problem is related to the 4.x kernel, since I have already tried another distribution with the kernel mermo and the problem persists. Using a windows virtual machine as guest works, which excludes communications and hardware issues.</p>
