Why do system updates take 30 minutes at full CPU speed?

by forthrin   Last Updated April 16, 2018 07:12 AM

Why do even minor system updates like 10.13.4 (requiring restart) take 15-30 minutes at full CPU speed (maximum fan speed, at least)?

Isn't a system update just rm <bunch of old files> and mv <bunch of new files>? This should be really fast even for a large quantity of files, and shouldn't require full CPU speed at all.

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