How can I remove modem-manager from boot?

systemctl disable ModemManager.service
systemctl stop ModemManager.service

This worked to disable UML-295 modem from being managed by ModemManger which in turn enabled web-control via http://mbb.vzw.com on CentOS 7.

Check after disabling via:

systemctl list-dependencies multi-user.target | grep Modem

The simplest way is to:

sudo apt-get purge modemmanager

Works fine in 12.04 LTS. Nothing in my system had dependencies on modemmanager.

Or you could search for "modemmanager" in the Ubuntu Software Center and remove it from there (the title is "D-Bus service for managing modems").

This it looks to work fine:

sudo mv /usr/share/dbus-1/system-services/org.freedesktop.ModemManager.service /usr/share/dbus-1/system-services/org.freedesktop.ModemManager.service.disabled

Instead this doesn't work ( don't know y ):

"echo manual | sudo tee -a /etc/init/modemmanager.override"