How can I disable hud-service?

Open a terminal and do

on 32bit system

sudo chmod -x /usr/lib/indicator-appmenu/hud-service

on 64bit system

sudo chmod -x /usr/lib/x86_64-linux-gnu/hud/hud-service

which removes - the execute mode x (i.e., permission) from hud-service.

Done.

You may want to gently end (or violently kill) the currently running hud-service (or reboot, etc) for "changes to take effect" immediately...

You may want to read this answer here on a similar thread:

https://askubuntu.com/a/693203/223872

The HUD is related to the Unity Launcher. For example it analyzes the files you are using and offers them when you press Super.

On my system (Ubuntu 15.10) the hud-service started using 100% of one CPU.

I solved this by installing Compiz Config Settings Manager (ccsm) and disabled all effects and set "Enable Low Graphics Mode" in "Ubuntu Unity Plugin":

sudo apt-get install compizconfig-settings-manager
ccsm

Although you can indeed disable the executable bit, when the system upgrades, it may reset that bit to on when the file is overridden on new updates.

Also, the comment above the one I posted above mentions that the hud-service is in the package hud, which if you just don't want, it might be better to just remove the package entirely.

https://askubuntu.com/a/699888/223872