I installed the Arduino IDE according to the arduino.cc instructions (invoking
install.sh) rather than
sudo apt install .... The ports
/dev/ttyACM* were present when the following Linux command is issued.
ls -l /dev/ttyACM*
This shows that the devices have membership in the
dialout group. It is necessary to add myself as a user to the group
sudo usermod -a -G dialout <username>
I selected the board and the port and did a download which eventually completed but it seemed to take a long time. The program probably wasn't working since the program was to flash an LED at a 2 second period but the flash rate was definitely much faster so it seems the download did not work.
I deleted the IDE and reinstalled and the ports disappeared.
I have applied this fix for using the Arduino IDE on Linux.
From the description of the fix the instruction is to issue the following commands:
wget https://github.com/adafruit/Trinket_Arduino_Linux/raw/master/99-adafruit-boards.rules sudo cp 99-adafruit-boards.rules /etc/udev/rules.d/
Next reboot Linux.
According to this page on Arduino for Linux there ought to be some devices at
/dev/ttyACM* but mine are missing. What is the solution to this problem? I have replaced the USB cable and it makes no difference.
The board is Adafruit Feather 32u4 which has an ATmega32u4. The OS is Ubuntu 16.04.