CHKDSK

chkdsk

A component of Microsoft Windows
Chkdsk.exe in action on drive C: in Windows 10
Details
Type	Utility software
Included with	DOS, OS/2 and Windows
Related components
Microsoft ScanDisk (Co-existed with Chkdsk in Windows 9x and MS-DOS 6.x)

CHKDSK (short for "check disk") is a system tool in DOS, OS/2 and Windows. It verifies the file system integrity of a volume and fixes logical file system errors. It is similar to the fsck command in Unix.

On Windows NT operating systems, CHKDSK can also check the disk surface for bad sectors and mark them. (In MS-DOS 6.x and Windows 9x, this is a task done by Microsoft ScanDisk.) Windows Server version of CHKDSK is RAID-aware and can fully recover data in bad sectors of a disk in a RAID-1 or RAID-5 array if other disks in the set are intact.

CHKDSK can be run from DOS prompt, Windows Explorer, Windows Command Prompt or Recovery Console.

On Windows NT family, a standard CHKDSK scan consists of three phases of testing file metadata. It looks for errors but does not fix them unless it is explicitly ordered to do so. Same applies to surface scan: This test, which could be extremely time-consuming on large or low-performance disks, is not carried out unless explicitly requested. CHKDSK requires exclusive write access to the volume to perform repairs.

Because of the exclusive access requirement and the time-consuming nature of CHKDSK operation, Windows Vista implemented a new file system health model in which the operating system fixes errors on the volumes as it encounters them. In the event that the problem is grave and a full scan is required, Action Center notifies the user to take the volume offline at the first convenience.