Using System File Checker (SFC) To Fix Issues

re: Using System File Checker (SFC) To Fix Issues

Drewfus — Wed, 09 Feb 2011 23:17:06 GMT

If a system had corruption of the Component Based Servicing stack, the type of corruption that the System Update Readiness Tool might fix or at least find, would this affect the operation of a command like 'sfc /scannow' ? Presumably SURT cannot be run offline, limiting the capacity of SFC to fix errors offline.

In general, would it be a good idea to run SURT and check %SYSTEMROOT%\Logs\CBS\CheckSUR.log, before running SFC.exe?

support.microsoft.com/.../947821

re: Using System File Checker (SFC) To Fix Issues

Christoph Wegener — Mon, 01 Feb 2010 10:33:31 GMT

It's probably futile to comment on such an old post, but I want to point out that the following statement is incorrect:

"From this you can tell that SFC compared the hash for fmifs.dll and found it wasn't correct. It restored the backup from c:\windows\WinSxS\x86_microsoft-windows-gmifs_31bf3856ad364e35_6.0.6000.16386_none_54d7af8934ac24f1

You missed the %Windir%\winsxs\BACKUP\.... part in the pathname.

Christoph Wegener

re: Using System File Checker (SFC) To Fix Issues

Janus Daniels — Sun, 24 May 2009 17:53:56 GMT

Please change your command line:

SFC.EXE /scannow /offbootdir:c:\ /offwindir=c:\windows

to a correct command line, like:

sfc /scannow /offbootdir=c:\ /offwindir=c:\windows

Please notice the : vs. = in the middle of the command. (This still assumes of course OS on C, etc.)

Thanks!

re: Using System File Checker (SFC) To Fix Issues

Tom Acker x-msft — Wed, 23 Apr 2008 01:47:10 GMT

When a hotfix, service pack or any other update is made to Windows Vista or Windows 2008, those changes are added to the component store located in %windir%\winsxs. The files that were updated are switched to an "off" state, and the new files are switched to an "on" state. The older files are never removed in the event that the driver, file, etc needs to be removed at a later date or in the event of an installation failure that requires the OS to rollback the changes made.

What happens when you run SFC is that we initially check the component store in %windir%\winsxs to ensure that a link to the file is correct based on the checksum of the file. If those checksums dont match, that file is projected back to the proper location in the %windir% directory. In the event that you are servicing the installation offline, such as in WinRE, you must specify the location of the Windows directory using the /offbootdir and /offwindir switches when running the SFC command, this allows us to find the component store and initiate a repair. Because Vista and 2008 are shipped in the .WIM format, there is no way for us to extract files from media as we did in downlevel operating systems. So you specify where you want files to be restored from and where they should be restored to with those switches.

NOTE: Only /scanfile and /scannow are considered repair operations, if you use /verifyfile or /verifyonly, no changes to the system will be made.

In the event that the component store file becomes corrupted, there is a backup for the ones marked boot critical in the %windir%\winsxs\backup directory and an attempt is made to rebuild the component store file and reproject it. If the files both the component store and the backup locations become corrupted, then a reinstallation or CompletePC backup would be the preferred method of resolving that issue.

re: Using System File Checker (SFC) To Fix Issues

anony.muos — Wed, 19 Dec 2007 14:05:37 GMT

What I'm most interested in is how SFC in Windows Vista handles files which have been updated by hotfixes/service packs, ESPECIALLY, when checking an offline Windows installation. Do the original unpatched files from the Windows DVD get restored or the updated ones from some backup? Where is the backup made?

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