Mouse pointer size inconsistent

This is actually a bug, however, there is a known solution.

First, edit your /etc/X11/Xresources/x11-common file:

sudo nano /etc/X11/Xresources/x11-common

Now, add this to or edit the file to include the following:

Xcursor.size: 22
Xcursor.theme: DMZ-Black

Known sizes are 8, 16, 22, 24, 32

Press CTRL + o and then press ENTER to save the file. Press CTRL + x to exit nano.

Log out and then log back in or restart your xsession to apply the changes.

Personally, I use Adwaita instead of DMZ-Black. Adwaita is a quite similar black cursor but has a different spinning icon for when the system is busy.

You can install it:

sudo apt-get install adwaita-icon-theme-full

Then, set the file like so:

Xcursor.size: 22
Xcursor.theme: Adwaita

source: bugs.launchpad.net

See this related answer for how to change the cursor size on certain applications.

EDIT : After further testing by undoing all my manipulations, I found out that the sudo update-alternatives --config x-cursor-theme command to choose one among cursors with manual mode was sufficient.

My mistake was that I only logged out from my session after each change. This wasn't sufficient. You have to reboot your system after this change !