Why is a system restart required on installing any patches OR any specific
software (E.g. Windows update)? Exactly What happens in the system during such
restart?
Have you ever run into the âFile In Useâ problem? You know, the one where
you canât delete a file because someone else is using it? Or perhaps youâve
encountered âdevice cannot be stopped right nowâ when trying to safely remove a
USB device?
Windows runs into exactly the same problems.
Only worse, actually.
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Windows update is, of course, about updating Windows itself â that much is clear.
There are two important things to realize about Windows:
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Itâs huge. Patches or updates actually only strategically update portions of Windows. The portions that are updated vary from patch to patch depending on what parts of Windows are considered to need immediate updating. Updating all of Windows at once is the stuff of service packs or completely new releases.
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Itâs just a computer program. Yes, itâs a big, complex and important computer program, but itâs a computer program nonetheless. In many ways a Windows computer program which means that itâs subject to all of the rules of Windows computer programs that it, itself imposes.
The rule that second point imposes is very simple: you canât make changes to a computer program while itâs running.
And some portions of Windows are always running.
The good news is that Windows is huge, and some portions â many portions perhaps â either arenât running or can be temporarily stopped so that they can be updated. When only these portions of Windows are updated, no reboot is required.
The other portions pose a problem.
The solution is a sequence that looks something like this (over simplifying somewhat, as usual) :
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Windows update notices that a file it wants to update is in use, and cannot be updated.
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The new version of the file is copied to a temporary location instead.
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Instructions are added to the system which are to be executed on the next boot.
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Windows Update informs you or annoys you with the message that a reboot is required â or if so configured just reboots the machine when itâs done.
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Windows reboots.
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As early in the boot sequence as possible, before the affected programs have begun to run, the instructions left behind delete or move the old version of the file to be updated, and replace it with the new one from the temporary location.
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The boot sequence then proceeds and the new version of the file is used.
The old version of the file may be preserved if the update can be reverted, otherwise itâs simply deleted.
Iâm sure youâve also seen updates that happen as the machine is shutting down â the same concept applies: components are updated after theyâve shut down as Windows shuts down, and Windows elects to update them as it closes so that when it starts up again the new versions will be in place.
Thereâs a lot of effort thatâs gone into reducing the number of reboots an update (or even an install) requires. Given the complexity of the software managing all the possible combinations and possible âin betweenâ states is a pretty large undertaking. By and large reboots now happen only when they really need to.
Even if that still seems to be more often than we might want.
What will happen if when Windows or any other software for that matter requires a reboot to update, but then I do not reboot until the very last minute then I just shut down the computer. Will the software be updated the next time I turn the computer on??
11-Jul-2010
If you donât update right away when asked it wonât harm anything. You can simply wait until you shut down to reboot. Some programs are friendly and let you know this. Others are written by more arrogant programmers who make you think your computer will suffer if you donât reboot immediately. MS is in the arrogant category and not only scares you but until recent versions would bug you every few minutes to reboot. Now at least they give you the option of postponing the warning for 4 hours.
Mark:
I learned long ago to simply not answer the âreboot now, or bug you again in 5 minutesâ dialog. Instead, I would drag the window as far to the edge of the screen as I could, leaving only a few pixels visible, and ignore it.
13-Jul-2010
The last dialog I saw went along the lines of âWindows IS rebooting in 15 minutesâ with a button for âreboot nowâ and one for âreboot laterâ. The only problem being, the âreboot laterâ button was greyed out.
Most of the time, this is not a problem, but if youâre in the middle of something that will take longer than 15 minutesâŠ.
It used to be said that Unix OS ( and Perhaps Linux too) do not have this Need to reboot for installing OS Updates, as an unvarying UNIX/Linux core/kernel keeps running, overlaid on which are the other and changeable /upgradable parts of the OS. So except for the rare kernel change, reboot is never needed for a Unix/Linux system. And definitely not needed for installing ANY Applications, whatever they be, WordProcessing, Spreadsheets, CAD and so on. Whereas Windows needs reboot for practically Every Application for completing the installation of that application.
Is it really true that all MS patches can be âinstalledâ on running system with no potential for bad behavior? I have anecdotes which suggest otherwise, especially if you wait a long time (months) before rebooting. I donât have any hard, repeatable proof of this sort of failure, but it seems to occur from time to time.