Where Is Chkdsk Stored for Reboot?

Chkdsk runs at startup in response to a "dirty bit" or registry setting.

Chkdsk is a file system error checking tool that can be run manually or automatically. If the operating system crashes or is shut down unexpectedly, a flag in the file system known as the "dirty bit" will be set. If chkdsk is set manually to run on the next system startup, it will make an entry in the Windows Registry.

The Dirty Bit

If the dirty bit has been set, its status can be seen with the "fsutil" command. Open a command prompt and type "fsutil dirty query C:" where "C:" is the drive or partition that you want to check. The command will return the message "Volume C: is dirty" or "Volume C: is not dirty."

Windows Registry Entry

When chkdsk is manually scheduled to run upon the next reboot, the value of the "BootExecute" entry in the "HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Session Manager" registry key will be changed. The default value is "autocheck autochk *." Scheduling chkdsk to check the "C:" drive upon startup will add "autocheck autochk /p \??\C:" to the entry.

Purpose

The reason for running chkdsk during the startup process is because this allows it to have exclusive access to the drive. Since chkdsk may need to make changes to the file system, it is essential that the operating system and other applications cannot write to the disk at the same time.

References

• Microsoft.com: Fsutil: Dirty
• Microsoft Support: Description of Enhanced Chkdsk, Autochk, and Chkntfs Tools in Windows 2000
• Windows 7 Forums: Disk Check