unumented DOS commands, Komputer, More Hacking [ Pobierz całość w formacie PDF ]
ࡱ; -!"#$%&'()*+,Root EntryFD7MatOSTD7MMMN0P@NDࡱ;FMicrosoft WorksMSWorksWPDocࡱ; NTGPOO^OOOO=/8dOOGCollection of undocumented and obscure features in various MS-DOS versions.---------------------------------------------------------------------------Contents:- TRUENAME- FDISK /STATUS- FDISK /MBR- SHELL=C:\COMMAND.COM /P /F- COMMAND /F- COMMAND /P- COMMAND /D- VER /R- ECHO OFF and ECHO ON- FORMAT /AUTOTEST- FORMAT /BACKUP- FORMAT /SELECT- FORMAT /SELECT /U- FORMAT /H- IF EXIST <dirname>\NUL <command> and IF EXIST EMMXXXX0 <command>- Using ATTRIB to hide directories- SWITCHES=/W- FOR %%V IN (/SOMETHING)- DIR,- COPY. A:- DOS?=HIGH- INSTALLHIGH- Using : for batch file comments- REM in lines with pipes or redirection- Delimiter character===========================================================================TRUENAME--------Internal DOS 5.0 command. Canonicalize a filename or path (using DOS interrupt 21h, function 60) prints the actual directory.Syntax:TRUENAME filename - Prints the complete path to file.TRUENAME directory - Prints the complete path to directory.Note: If the path is in a network, it starts with a \\machine-name.TRUENAME is analogous to the UNIX "whence" command. It returns the real fully-qualified path name for a command.TRUENAME is useful in networks, where a physical drive may be mapped to a logical volume, and the user needs to know the physical location of the file. It ignores the DOS SUBST and JOIN commands, or network MAPped drives.TRUENAME is an undocumented MS-DOS feature, but it is documented in JP Software's 4DOS software (COMMAND.COM replacement) as follows:Syntax:TRUENAME [d:][path]filenamePurpose:Returns a fully qualified filename.Comments:TRUENAME will see "through" JOIN and SUBST commands, andrequires MS-DOS 3.0 or above.Example:The following command uses TRUENAME to get the true pathnamefor a file:c:\>subst d: c:\util\testc:\>truename d:\test.exec:\util\test\test.exeTRUENAME : will reveal the full name drive and path of the filename. If you specify a wildcard (*) in the filename, it will expand the filename to use question marks instead. If the path includes the ..\ sequence, TRUENAME will examine the directory structure and calculate the path.Stranger still, the line:TRUENAME \CRONK\FLIBBET\..\ART...produces the response:C:\CRONK\ART...even if the directories \CRONK\FLIBBET and the file ART don't exist! Don't expect this command to work well across networks. After all, this is still undocumented in MS-DOS for a reason!===========================================================================FDISK /STATUS-------------Prints a screen just like using option 4 of FDISK, "Partition information", but includes extended partition information. Nice if you want to get an overview without fear of pressing the wrong keys.Doesn't work in DOS 3.30.===========================================================================FDISK /MBR----------MS-DOS 5.0 FDISK has an undocumented parameter, /MBR, that causes it to write the master boot record to the hard disk without altering the partition table information. While this feature is not documented, it can be told to customers on a need-to-know basis.Warning: Writing the master boot record to the hard disk in this manner can make certain hard disks partitioned with SpeedStor unusable. It can also cause problems for some dual-boot programs, or for disks with more than 4 partitions. Specific information is below.What is the MBR?At the end of the ROM BIOS bootstrap routine, the BIOS will read and execute the first physical sector of the first floppy or hard drive on the system. This first sector of the hard disk is called the master boot record, or sometimes the partition table or master boot block. At the beginning of this sector of the hard disk is a small program. At the end of this sector is where the partition information, or partition table, is stored. This program uses the partition information to determine which partition is bootable (usually the first primary DOS partition) and attempts to boot from it.This program is what is written to the disk by FDISK /MBR and is usually called the master boot record. During normal operation, FDISK only writes this program to the disk if there is no master boot record.Why is the MBR changed during Setup?During installation of Microsoft MS-DOS 5 Upgrade, Setup will replace the master boot record on the hard disk with code to display the message:The MS-DOS 5.0 Setup was not completed.Insert the UNINSTALL #1 diskette in drive A.Press the ENTER key to continue.This message should be erased and the master boot code rewritten before Setup is completed. If a problem occurs during Setup and you return to the previous MS-DOS, UNINSTAL should also remove this message. However, should Setup or UNINSTAL fail to remove this message, or should the master boot record become corrupted, a new master boot record can be written to the disk using the following command:C:\>fdisk /mbrWARNINGS:This option should not be used if:- the disk was partitioned using Storage Dimensions'SpeedStor utility with its /Bootall option- more than 4 partitions exist- certain dual-boot programs are in useStorage Dimensions' SpeedStor utility using the /Bootall option redefines the drive's physical parameters (cylinder, head, sector). /BOOTALL stores information on how the drive has been changed in an area of the master boot record that MS-DOS does not use. FDISK /MBR will erase that information, making the disk unusable.Some older OEM versions of MS-DOS and some third-party partitioning utilities can create more than 4 partitions. Additional partition information is commonly stored information on partitions in an area that FDISK /MBR will overwrite.Some dual-boot programs have a special MBR that asks the user which operating system they want on bootup. FDISK /MBR erases this program. Dual-boot systems that boot whichever partition is marked Active are not affected by FDISK /MBR.If you have a Boot Sector Virus, just boot from a known "clean" floppy disk that's write protected and which has FDISK on it, and run FDISK /MBR.===========================================================================SHELL=C:\COMMAND.COM /P /F--------------------------The /F in the CONFIG.SYS SHELL= statement forces a "Fail" response to all "Abort, Retry, Fail" prompts issued by the DOS critical error handler.===========================================================================COMMAND /F----------Entered on the command line, COMMAND /F makes all those annoying "Abort, Retry, Ignore, Fail" disk error messages default to "Fail" from then on until rebooting.===========================================================================COMMAND /P----------For DOS 3.30 (not checked with other versions): Docs say that this doesn't allow you to exit back to the previous shell, but /P also forces AUTOEXEC.BAT to be run on seco... 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