TrueRNG Notice: modemmanager package (and udev rules updated)

While testing out different Linux distributions with the TrueRNG, we stumbled upon an issue regarding the package ‘modemmanager’ that appears to be installed by default on my ‘ubuntu-style’ distributions.

This is happening because the TrueRNG appears as a CDC-ACM (serial port), this package is trying to scan the port and determine if it is a modem it can communicate with.  This is a problem because for the first 30 seconds, the package has changed the termios settings (set by the udev rules) and turns on xon/xoff flow control.  This means there is slight drop in uniformity / character distribution because the xon/off characters are being blocked by Linux until modemmanager gives up.

We have updated our udev rules that inform the modemmanager package to ignore the TrueRNG.  (Updated file here)

You can also just remove modemmanager if it is installed.



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