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What is CHKNTFS?

Most admins are familiar with CHKDSK, but what about it's lesser known cousin, CHKNTFS?


What is CHKNTFS?
Serdar Yegulalp

Most system admins are familiar with CHKDSK, the Windows NT/2000 utility used for checking the integrity of a volume. But they are often less familiar with CHKDSK's cousin, CHKNTFS.

CHKNTFS modifies the behavior of the Autochk program, run at boot-time, to prevent CHKDSK from running automatically if Windows automatically schedules it due to an improper shutdown. If the system still has data to write to a given volume, the volume's "dirty bit" is set. The dirty bit is a flag that indicates there was still data to be written to that volume, so the presence of a set dirty bit at boot-time indicates there may have been some sort of a problem with the shutdown.

CHKNTFS is also useful for disabling CHKDSK /F if it's been set to run on the next reboot. This is useful if you have scheduled a CHKDSK at one point, but need to reboot and don't want to deal with running CHKDSK at this time.

CHKNTFS has these options:

/C <volume>    Runs CHKDSK at the next reboot on the listed volume, but only if the dirty bit has been set.

/D    Runs CHKDSK on any drives that have the "dirty" bit set at the next reboot. This basically resets CHKDSK to its default behavior.

/X <volume>    Excludes a specified drive from boot-time checking, but only for the next reboot.

You can specify multiple volumes in each command, such as CHKNTFS /C C: D:

CHKNTFS works by changing the registry key BootExecute in HKEY_LOCAL_MACHINESYSTEMCURRENTCONTROLSETCONTROLSession Manager. The default value is a REG_MULTI_SZ value of autocheck autochk *.

Serdar Yegulalp is the editor of the Windows 2000 Power Users Newsletter.

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