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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.

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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

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Code or program output

Windows File Protection

Using File Signature Verification

Driver Signing for Windows

Command-line reference A-Z