MAAS can specify kernel boot options to machines on both a global basis (UI and CLI) and a per-machine basis (CLI-only). A full catalogue of available options can be found in the Linux kernel parameters list^ at kernel.org^.
To set kernel boot options globally, as an admin, open the ‘Settings’ page and on the ‘General’ tab scroll down to the ‘Global Kernel Parameters’ section:
Type in the desired (space separated) options and click ‘Save’. The contents of the field will be used as-is. Do not use extra characters.