A raging controversy over whether Windows patches ever reboot a PC without permission has been solved. Reboots can happen when you’re not expecting it — but you can minimize the problem or eliminate it entirely.
This subject sparked a debate when reader Evan Katz wrote in to ask whether Microsoft patches had started rebooting Windows automatically, even when the Automatic Updates control panel is configured to notify the user of downloads instead of installing them without notice. His comments were printed in the paid version of our Dec. 15, 2005, newsletter.
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I’ve found that there are several little-known cases in which a Microsoft patch can trigger a reboot when you’re not expecting it. No, my findings don’t support a conspiracy theory — Microsoft hasn’t deliberately changed its patches to make you lose your unsaved work in surprise reboots. The true answer lies within the secrets of Windows.
How patches can automatically reboot
In my research, I interviewed Mike Cook, a security support engineer in Microsoft’s Product Support Services (PSS) team. We turned up several reasons why a PC that requires a reboot might do so without warning:
1. Settings in the Automatic Updates control panel. The default for Automatic Updates is "Automatically download recommended updates for my computer and install them every day at 03:00," or whatever time is specified. If this option is selected, patches will be downloaded from the Microsoft site in the background and installed automatically at the specified time, after a 5-minute countdown is displayed. Re-installing Windows or some Windows components can silently reset Automatic Updates, making reboots happen without user intervention.
2. “Helpful” security add-ons. Some Microsoft programs can reset Automatic Updates to its most automatic option. The beta of Microsoft’s Windows OneCare Live security program, for example, notifies the user upon installation that this will be done, but this can easily be overlooked.
3. Windows Server Update Services (WSUS). Windows patches can be pushed to PCs on a network via WSUS, a server program from Microsoft. If so, a particular update can be assigned an installation deadline by an IT admin. “When an update is set to a deadline,” says Microsoft’s Cook, “it overrides any client configuration settings.” This can make a PC reboot even if an end user has Automatic Updates set to not automatically install patches. The PC would display a countdown, but if the user is away from the machine, the timer wouldn’t be seen before the reboot.
4. 10-minute reboot reminders. I believe this is the most common cause of reboots that aren’t expected. When you install Windows patches, and they require a reboot, you’re shown a dialog box asking whether you wish to “Restart Now” or “Restart Later.” (See Figure 1.) If you press the letter N, the reboot starts immediately. Pressing L closes the dialog box. But the default time for the dialog to re-appear is every 10 minutes.
Figure 1. Typing the letter N reboots Windows, even if you didn’t notice that the “Restart Now” dialog box was even on the screen.
“We had a lot of feedback on this during the beta” of Windows XP, says Cook. Microsoft’s developers decided that it was very important that a PC be rebooted after applying patches that require it, he indicates. So the decision was made to display a reminder every 10 minutes until the reboot was permitted by the user. And the dialog box was made “modal,” which means it grabs the keyboard focus and won’t go away until you press a key or close its window.
This may be the cause of a lot of “automatic” reboots. If you’re typing a document in, say, Microsoft Word, you could easily type the letter N without noticing that the dialog box had appeared. Whoops, there goes a reboot.
Despite the importance of reboots for certain patches, Cook is certain that Microsoft hasn’t changed the expected behavior. "If Automatic Updates is set to ‘Let me choose when to install,’ the machine should never reboot without an explicit user action," he says.
It can be very inconvenient if Windows reboots when you don’t expect it. Some applications will ask you to save your work, but others will lose work you may have spent a significant amount of time on. In either case, you have to kill some time while the reboot completes.
On the other hand, you don’t want to entirely forget to reboot after applying Windows patches. “It’s pretty important that the machine be rebooted, especially servers,” says Cook. “It could leave a machine in an unstable condition, being half-patched.” Applying a patch changes some files on disk, while others can’t be changed until the reboot occurs.
How to stop unexpected reboots
If you use Windows XP Pro, you can use a little-known setting to turn off the auto-reboot feature of Automatic Updates. This way, you can configure Automatic Updates to download and apply patches automatically at night, which is good for your security. But AU won’t reboot your PC. Instead, a reminder to reboot will be displayed. If you set AU to apply patches at 3:00 a.m., which is the default, you can reboot first thing in the next morning when you’re not in the middle of a project.
The best way to change this setting is using Windows XP Pro’s built-in Group Policy Editor (it doesn’t exist in XP Home):
Step 1. Click Start, Run, enter gpedit.msc, then click OK.
Step 2. In the window that opens, click the plus signs in the left pane to navigate to the following folder, then select that folder:
Computer Configuration Administrative Template Windows Components Windows Update
Step 3. In the right pane, right-click No auto-restart for scheduled Automatic Updates installations, then click Properties. In the Properties dialog box that appears, select Enabled, then click OK and close the Group Policy Editor window. You’re done.
Microsoft provides information about this and several other options in Knowledge Base article 328010.
Use WSUS to stop 10-minute reminders
If your company uses Windows Server Update Services to distribute patches, you can take advantage of a little-known setting in the Windows Registry to prevent the 10-minute reminders. With WSUS installed, you can change the interval from 10 minutes to as long as 1440 minutes (24 hours).
I don’t recommend that you set the option to 24 hours, however. If someone dismisses a reminder, and then forgets to reboot before leaving the PC for the night, another reminder could pop up exactly when they’re working hard the next day. The problem of accidental "Restart Now" commands would be as bad as before.
Instead, I recommend that you set the Registry to remind you every 12 hours (720 minutes). This way, if a reminder is dismissed, the next dialog box will pop up when no one is likely to be working at the PC. (Anyone who types for 12 hours without a break has bigger problems than unexpected reboots.)
If WSUS is installed, the reboot-reminder time is specified in the following Registry subkey:
HKEY_LOCAL_MACHINE Software Policies Microsoft Windows WindowsUpdate AU
The key that controls the delay is RebootRelaunchTimeout. Set this to 720 for 12 hours, or whatever interval you wish.
Microsoft has documented this and several other Automatic Update configuration settings for non-Active Directory environments in a TechNet article. That article mentions that your RebootRelaunchTimeout setting will be ignored if you set RebootRelaunchTimeoutEnabled to 0.
For a description of how to use Group Policy Objects in an Active Directory environment to set the interval, see Microsoft’s article on AU by Group Policy.
Whew. All this work just to make sure that a reboot won’t take place without your active participation! It’s complicated, but I’ve tried in this article to give you the basic facts you need and links to more.
To send us more information about the reboot-reminder problem, or to send us a tip on any other subject, visit WindowsSecrets.com/contact. You’ll receive a gift certificate for a book, CD, or DVD of your choice if you send us a comment that we print.
Brian Livingston is editor of the Windows Secrets Newsletter and the coauthor of Windows 2000 Secrets, Windows Me Secrets, and eight other books.