Check Disk - check and repair disk problems
CHKDSK [drive:][[path]filename] [/F] [/V] [/R] [/L[:size]]
[drive:] Specify the drive to check.
filename Specify the file(s) to check for fragmentation (FAT only).
/F Automatically Fix file system errors on the disk.
/R Scan for and attempt Recovery of bad sectors.
/V Display the full path and name of every file on the disk.
/L:size NTFS only: change the log file size to the specified number of
kilobytes. If size is not specified, displays the current log size and
the drive type (FAT or NTFS).
/C Skip directory corruption checks.
/I Skip corruption checks that compare directory entries to the
file record segment (FRS) in the volume's master file table (MFT)
CHKDSK c: /F
Fixing Errors /F
If the drive is the boot partition for NT, you will be prompted to run the check during the next boot. To issue chkdsk on a hard drive you must be a member of the Administrators group. If you specify the /f switch, chkdsk will show an error if open files are found on the disk.
If you use chkdsk /f on a very large disk or a disk with a very large number of files (millions), chkdsk may take a long time to complete. The computer will not be available during this time, as chkdsk does not relinquish control until it is done.
Scanning only (without the /f switch)
If a file needs to be fixed chkdsk will alerts you with a message but will not fix the error(s). Chkdsk may report lost allocation units on the disk - it will produce this report even if the files are in-use (open). If corruption is found, consider closing all files and repairing the disk with /F. Often the easiest method (even for non-primary partition drives) is to run the scan during bootup.
Cluster (or block) Size
CHKDSK produces a report that shows the the block /cluster size
"4096 bytes in each allocation unit."
0 No errors were found
1 Errors were found and fixed.
2 Could not check the disk, did not or could not fix errors.
It is possible to run CHKDSK on a live system (as long as /f is not specified), a good strategy is to schedule an AT job to detect any disk problems by running CHKDSK >LogFileOfErrors.txt - then check the log files and manually fix any problems only as they occur.
When CHKDSK is set to run at boot-up there is a delay to allow the check to be cancelled - this can be configured in the registry:
The value is the time in seconds that you want CHKDSK to wait (0 = no delay) default is 10 seconds.
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