Tip of the Week 5 – When sfc fails, DISM prevails

In the last month or so, I have come across a number of servers where the only possible cause remaining for the “issues” is file system/OS corruption. This has been across various scenarios; Cloud hosted, on premise physical, on site virtualised etc. and each time the obvious Googleable thing to try is a sfc /scannow.

For those who do not know this command, it is an old, old, old Windows built in tool designed to scan and repair corruption within Windows itself, notable directories such as System32. File system corruption can occur for many reasons, a dodgy build of the OS to start with, Windows Update issues, potentially caused even by viruses, or remnants of. So the cool thing about running sfc /scannow (from an elevated Command Prompt), is that it is has been around since Windows 98 – incidentally my first OS on a PC that was solely mine!

So sure, I have run this many times, probably more than a hundred, but recently on more advanced operating systems such as 2012R2 and 2016, I have seen it failing a little. Usually the result of the scan states

“Windows Resource Protection found corrupt files but was unable to fix some of them

Details are included in the CBS.Log windir\Logs\CBS\CBS.Log.”

So if you see this does it mean your system is totally broken…

 
 

All is not lost

 
 

If you have seen my previous posts on DISM you will know it is great for keeping a system tidy, especially when it comes to Windows Updates and the bits they leave behind. However, did you know that DISM could also be used to repair the file system? – Well no, neither did I until this year!

There are a couple of commands very useful to try, when a sfc fails:

  • DISM /Online /Cleanup-Image /CheckHealth

    This checks for corruption without attempting repair

  • DISM /Online /Cleanup-Image /ScanHealth

    This checks for Windows Image corruption and takes significantly longer than a CheckHealth

  • DISM /Online /Cleanup-Image /RestoreHealth

    BINGO! – this one will actually attempt the repair of a corrupted filesystem, and from experience means an sfc /scannnow will also complete without errors.

     
     

 
 

Please note I am not saying this is the solution to all file system/OS corruption, what I’m saying is in the last few weeks it has saved 3 servers from being binned!

 
 

So yet again, system maintenance via the DISM tool is a winner, whether keeping it tidy or just in one piece.