You can modify certain parameters of the mouse driver permanently, i.e. accross reboots.
First list Xorg input devices.
Results are for my present machine and will be different in yr case.
List Xorg session input devices in terminal (CRTL-ALT+T):
$ xinput --list
⎡ Virtual core pointer id=2 [master pointer (3)]
⎜ ↳ Virtual core XTEST pointer id=4 [slave pointer (2)]
⎜ ↳ SynPS/2 Synaptics TouchPad id=10 [slave pointer (2)]
⎜ ↳ PS/2 Generic Mouse id=11 [slave pointer (2)]
⎣ Virtual core keyboard id=3 [master keyboard (2)]
↳ Virtual core XTEST keyboard id=5 [slave keyboard (3)]
↳ Power Button id=6 [slave keyboard (3)]
↳ Video Bus id=7 [slave keyboard (3)]
↳ Sleep Button id=8 [slave keyboard (3)]
↳ AT Translated Set 2 keyboard id=9 [slave keyboard (3)]
↳ HP WMI hotkeys id=12 [slave keyboard (3)]
So my mouse is identified by: "PS/2 Generic Mouse" and has identifier 11. For you it might be different.
Next, to list the mouse properties, do in terminal:
$ xset q | grep -A 1 Pointer
acceleration: 2/1 threshold: 4
To experiment with zero mouse acceleration parameters,use:
$ xset m 0/1 4
Your device may have other parameters values. You can experiment with them until you are satisfied with the result. Doing so with the cli utility
xset allows you to tweak the device parameters on the fly, i.e. without restarting the Xorg session. However those settings will not be preserved across reboots.
You need to make them persistent (until the next driver or system upgrade), by creating a new file in
/usr/share/X11/xorg.conf.d/. For instance:
$ cd /usr/share/X11/xorg.conf.d
$ sudo vim 80-mouse-accel-disable.conf
Identifier "Set mouse acceleration to zero"
# Default value of mouse acceleration: 2/1 4
# Set AccelerationNumerator to zero to disable
Option "AccelerationNumerator" "0"
Option "AccelerationDenominator" "1"
Option "AccelerationThreshold" "4"
$ sudo chmod 644 80-mouse-accel-disable.conf
That's it. You can logout and back in or reboot. In principle yr mouse acceleration should be persistently set to 0.
As suggested in one of the comments below, the above may only apply to Ubuntu 14.04 and derived flavors. In later versions the config file syntax and keywords may change slightly, although the general principle of the solution remains valid. See this tip for version 16.04 and (perhaps) later (not tested by me).