System File Checker (sfc)
Scans and verifies the versions of all protected system files after you restart your computer.
Syntax
sfc [/scannow] [/scanonce] [/scanboot] [/revert] [/purgecache] [/cachesize=x]
Parameters
/scannow : Scans all protected system files immediately.
/scanonce : Scans all protected system files once.
/scanboot : Scans all protected system files every time the computer is restarted.
/revert : Returns the scan to its default operation.
/purgecache : Purges the Windows File Protection file cache and scans all protected system files immediately.
/cachesize=x : Sets the size, in MB, of the Windows File Protection file cache.
/? : Displays help at the command prompt.
Remarks
| • | You must be logged on as a member of the Administrators group to run sfc. |
| • | If sfc discovers that a protected file has been overwritten, it retrieves the correct version of the file from the %systemroot%\system32\dllcache folder, and then replaces the incorrect file. |
| • | If the %systemroot%\system32\dllcache folder becomes corrupt or unusable, use sfc /scannow, sfc /scanonce, or sfc /scanboot to repair the contents of the Dllcache directory. |
Formatting legend
| Format | Meaning |
Italic | Information that the user must supply |
Bold | Elements that the user must type exactly as shown |
Ellipsis (...) | Parameter that can be repeated several times in a command line |
Between brackets ([]) | Optional items |
Between braces ({}); choices separated by pipe (|). Example: {even|odd} | Set of choices from which the user must choose only one |
Courier font | Code or program output |
Using File Signature Verification