CHKDSK--Notes

Format of status reports

MS-DOS displays CHKDSK status reports similar to the following example:

    Volume Serial Number is B1AF-AFBF

     72,214,528 bytes total disk space
         73,728 bytes in 3 hidden files
         30,720 bytes in 12 directories
     11,493,376 bytes in 386 user files
         61,440 bytes in bad sectors
      6,055,264 bytes available on disk

          2,048 bytes in each allocation unit
         35,261 total allocation units on disk
         29,568 available allocation units on disk

        655,360 total bytes memory
        493,456 bytes free

Fixing disk errors

The ScanDisk program is the preferred method of fixing disk errors. For more
information, see the <SCANDISK> command.

If you want to use CHKDSK to fix disk errors, use the /F switch. (CHKDSK
corrects disk errors only if you specify the /F switch.) CHKDSK /F displays
a prompt similar to the following:

    10 lost allocation units found in 3 chains.
    Convert lost chains to files?

If you press Y, MS-DOS saves each lost chain in the root directory as a file
with a name in the format FILEnnnn.CHK. When CHKDSK finishes, you can
examine these files to see if they contain any data you need. If you press
N, MS-DOS fixes the disk but does not save the contents of the lost
allocation units.

If you do not use the /F switch, CHKDSK alerts you with a message if a file
needs to be fixed but does not fix the error(s).

Using CHKDSK with open files

Never use CHKDSK when files are currently open. CHKDSK is designed for use
when the files on the disk are in an unchanging state -- that is, when they
are not open. When a file is open, it is probably changing, and MS-DOS will
update the file allocation table and the directory structure to reflect
changes. Such updates are not always made immediately, and updates to the
file allocation table and the directories occur at different times. If you
run CHKDSK when files are open on the disk, it interprets differences
between the directory structure and the file allocation tables as errors.
Running CHKDSK /F when files are open can result in corruption or loss of
data. Therefore, never run CHKDSK /F from another program, or when Microsoft
Windows or the MS-DOS Task Swapper is running.

Using CHKDSK with assigned drives and networks

The CHKDSK command does not work on drives formed by the SUBST command. You
cannot use CHKDSK to check a disk on a network drive.

Physical disk errors

The CHKDSK command finds only logical errors in the file system, not
physical disk errors. To identify and repair physical disk errors, use the
ScanDisk program. For more information, see the <SCANDISK> command.

Bad disk sectors

Bad sectors reported by CHKDSK were marked as "bad" when your disk was first
prepared for operation. ScanDisk and other physical disk-error correction
utilities can also mark sectors as "bad." Bad sectors pose no danger.

Cross-Linked Files

CHKDSK reports a cross-linked file if two files or directories are recorded
as using the same disk space. If CHKDSK finds a cross-linked file, it
displays a message similar to the following:

    <File is cross linked on allocation unit <number>

Some of the information in these files or directories has been lost.

CHKDSK will not fix a cross-linked file, even if you specify the /F switch.
To correct a cross-linked file, run ScanDisk. Or, to fix them manually, copy
the specified files or directories elsewhere and delete the originals.

ERRORLEVEL parameters

If CHKDSK does not find any errors, it returns an ERRORLEVEL value of 0. If
CHKDSK found one or more errors, it returns an ERRORLEVEL value of 255.

Saving a CHKDSK status report to a file

You can save a CHKDSK status report by redirecting the output to a file. Do
not use the /F switch when you redirect CHKDSK output to a file.