I got a Logitech MX Master mouse recently, and I wanted to share my experience getting it working under Linux.

I had a program called Solaar installed before I got the mouse, and Solaar detected the mouse and paired it with my existing wireless receiver right away. However, in order to disable the auto-shift mechanism that switches from ratcheted scrolling to smooth scrolling at a certain speed, I had to uninstall the default version of Solaar in my distribution's repository (0.9.2-5 in Arch) and install a newer version from GitHub (listed in Arch as version "20151002-1"). The newer version has several new features. One of them is a "Smart Shift" slider, where you can set the sensitivity of the auto-shifting, or set the scroll wheel to always free-scrolling or always ratcheted by putting the slider all the way to either side. Another new feature not present in 0.9.2 is a "dpi" setting, where you can adjust the resoltuion the mouse's sensor uses (lower DPI makes the mouse move slower, higher DPI makes the mouse move faster).

The horizontal scroll wheel works out of the box (although not as many applications support it as I expected). However, I wanted to flip the direction of the horizontal scrolling– the default direction felt wrong to me. To achieve that, I used the "xinput" command. You can type "xinput –list" to get a list of all the mice (and keyboards) your computer detects. To reverse the scroll direction for the horizontal wheel only, I ran "xinput -–set-button-map 'Logitech MX Master' 1 2 3 4 5 7 6". Notice that the 7 and 6 are flipped– if you typed them in the correct order, the mouse would use the default directions. My guess is that 1=left click, 2=right click, 3=middle click, [4=scroll up, 5=scroll down]*, [6=scroll left, 7=scroll right]*. *may be flipped

By the way, before I went through all of that trouble, I did manage to get a virtual machine to detect the Unifying receiver and the MX Master, and I set all the settings I wanted in the VM. Unfortunately, the settings aren't saved on the mouse, but on the computer, so once I exited the VM, everything was back to the default behavior. That's why we're going with all Linux-native tools here.

Right now, the button below the scroll wheel switches between ratcheted and smooth scrolling, and clicking the scroll wheel itself is the middle click. In the near future, I may look into swapping that, possibly with xinput, just to improve the longevity of the mouse (I've heard people saying the ratcheted scrolling can break, and that's one of the reasons I wanted to disable Smart Shift, too.)

As an update, I don't have Solaar installed on my laptop, but the mouse did keep the no auto-shift setting. Also, the mouse takes a second or two to turn on when it's using Bluetooth, but it's just about instant when using the USB adapter.