Beginning with the 2.0.0-2 update, system updates are automatically downloaded via the NIM module. The system only downloads updates, Home Menu will only finalize update installation once the user gives permission for that(via the “Install system update” dialog). Each time the event handle from NIMU command 0x00050000 is signaled, Home Menu uses NIMU:GetState and NIMU:CheckSysupdateAvailable to check whether a system update is available. When an update is available Home Menu will then set some Home Menu state flags, which likely indicate that the “Install system update” dialog should be shown.
The system checks for updates every 24 hours, then downloads all updated titles if an update is available. This is the same as doing a system update via System Settings, except with this the update installation will not be finalized until Home Menu uses the NIMU:FinishTitlesInstall command.
It is possible to erase this update data by entering the Recovery Mode.