What is ModemManager?
In Ubuntu (and most modern Linux distributions), ModemManager is a background service (daemon) designed to handle mobile broadband connections. If your laptop has a built-in 4G/LTE cellular modem, or if you plug in a 5G USB dongle, ModemManager detects the hardware, reads the SIM card, and communicates with the cellular network to provide you with internet access.
However, if you are running Ubuntu on a standard desktop PC, a home server, or a Wi-Fi-only laptop, you do not have any cellular hardware. Despite this, the ModemManager service starts automatically on every boot and continues running in the background, consuming a small amount of RAM and occasionally probing serial ports for non-existent modems (which can sometimes interfere with Arduino devices or serial console cables). You can safely disable this service.
How to Disable ModemManager in Ubuntu
To prevent the service from running, you must disable it using systemctl.
- Open your Ubuntu Terminal (shortcut:
Ctrl + Alt + T). - Stop the service immediately for the current session:
sudo systemctl stop ModemManager.service- Disable the service so it does not launch on the next system boot:
sudo systemctl disable ModemManager.service- (Recommended for Desktop Users): If you know you will never, ever use a 4G/5G cellular connection on this specific computer, the cleanest option is to completely remove the package:
sudo apt-get purge modemmanagerDisabling or removing this service will have absolutely zero effect on your standard Ethernet or Wi-Fi connections, as those are handled separately by NetworkManager.