What is happening on startup after system update?

[hazmat]

So after an update or something, the computer on reboot will sit at the grey Apple screen with progress meter for a LONG time. What exactly is taking so long?

[rgbrock1]

I had the same thing happen to me after I upgraded to 10.2.1.
However, all subsequent reboots were much faster. I guess immediately after the upgrade - first reboot after - the Operating System is doing something which it doesn't subsequently do.

[hazmat]

Exactly. But I want to know what, exactly. I see this happen sometimes also if I make a change to some system files and reboot. I don't think it's optimizing, since it does that after the update, before reboot. I have to remember next time to do a verbose boot....

[fryke]

Just a guess, but it's likely that some links have to be updated. I guess the fast startup speed we see in Jaguar (and other operating systems) stem from the fact that the OS 'knows' from the last time what will happen. (Doesn't sound very technical, but I hope you know what I mean.)

Now after a system update - or maybe if you changed some system files by hand - the OS notices that its expectations fail and first has to look for things it otherwise would find in the expected places (I don't mean files, I mean places *in* files).