Windows patch What's the difference between GDR and QFE?

When installing Windows patches, you will often see the words "GDR" or "QFE" in the patches, what do they mean? It turns out that Microsoft has classified the update system files in the patch, where the GDR represents the "normal distribution version" and qef the "Quick Fix Engineering Update" (Quickfix Engineering). GDR update files generally have a lot of rigorous testing, so the stability of the patch is relatively high, while the QFE update files generally do relatively little testing, so its stability is not as good as the GDR.

Windows patches are divided into two categories: a class called "Security Patches," which includes both GDR and QEF versions of the update files, which are two replicas that are typically released for critical updates when Windows is found to be a critical vulnerability, and the second is called "hotfix." Typically, some non-critical updates contain only the QFE version of the update file.

Why does the security patch include two versions of the update file? For example, now install a non-critical update that contains only the QFE version of the file. If this patch needs to be updated the old system file is already GDR edition, the update automatically compares the version number of the old and new files, and if the original GDR file version is higher than the Qef file version in the patch package, it automatically disables the update of the QFE file in the patch package and instead changes to the original GDR The file version number is the same QEF version of the file to update. So where do I find this QFE file with the same version number as the original GDR file? The actual file is already on the computer's hard drive because the same version of QFE has been copied to the system for the last time you installed the security patch that contains the GDR file. This is why the security patch contains two copies of the GDR and QFE.

As an example: Install the KB896688 patch, this patch needs to update the system file%systemroot%\system32\mshtml. Dll. Because the KB89668 patch is a "security patch," it includes both GDR and QEF versions of the MSHTML version two. DLL copies, and their file descriptions are "xpsp_sp2_gdr.051004-1415" and "xpsp.051004-1419" respectively. After the update is executed, the installer automatically detects the MSHTML of the current system. DLL version, if the original file is found to be the GDR version, it will be updated with the GDR version of the patch package, if the original file is found to be QEF version, it will be updated with the QFE version of the patch package. In either case, after the update, the new system files will be updated 6.00.2900.2769 new version number, but only the GDR and the QFE points.

Now, let's go back to the first example mentioned earlier with the example of KB896688. Suppose we update the KB896688 patch before the original system file MSHTML. DLL is already a GDR version, then when updating patches, the GDR version of the xpsp_sp2_gdr.051004-1415 version of MSHTML is used. DLL for updates. At the same time, the update copies the xpsp.051004-1419 Qef file to the hard disk, which is the $HF _mig$ subfolder under the Windows folder. Let's say we need to install one later and need to modify MSHTML. DLL's other non-critical patches, this patch automatically detects which version of the Qef file it provides is higher than the xpsp_sp2_gdr.051004-1415. If you provide the QEF version is not as high as the xpsp_sp2_gdr.051004-1415 version, it will not be updated with their QFE files, but will be from the windows\ $HF _mig$ take the spare xpsp.051004-1419 out, be updated.

Remember someone once asked if the $hf_mig$ folder under Windows in the System folder can be deleted. Now after the explanation of the above should understand, it is better not to casually delete windows\ $hf _mig$ folder. Deleting this folder will not cause the system to crash immediately, but once that happens, there may be a compatibility issue that can result from a system file version mismatch after the installation of a new patch. Therefore, do not easily delete the $hf_mig$ folder.

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