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DOS Command Line Switches |
DOS Command Line ParametersThese are primarily the uncommon and undocumented switches Click the appropriate tab to display the switches that can be used with that particular command. DOS command switches are always preceded with a forward slash (/) and there is always a space between the command and the first switch. You must press the Enter key before the command will be executed. Take note that many of these switches or combinations thereof have warnings attached. When you see a warning, read and heed. |
| Command (command.com) this is the basic command interpreter | |
| Command /D /F /T | |
| /D | (Deny) Performs different actions depending on the MS-DOS version:
[MS-DOS 5.00 and above ONLY] |
| /F | (Fail) Removes the "Abort, Retry, Fail" message and forces a "Fail" response to all "Abort, Retry, Fail" prompts issued by the DOS critical error handler. If the floppy disk is not ready it automatically goes to "Fail".
[MS-DOS 6.00 and above ONLY] |
| /T | Forces the COMMAND.COM resident module to load permanently in low memory (below the 640K barrier), even if the Upper Memory Area (UMA) is enabled by an upper memory manager (i.e. EMM386.EXE or UMBPCI.SYS) from CONFIG.SYS. Using /T in combination with the /P (PERMANENT) parameter, ONLY from the DOS prompt or in batch files (NOT from the CONFIG.SYS SHELL= line), also executes the AUTOEXEC.BAT file (if present), besides forcing the COMMAND.COM resident module to load permanently in low memory. WARNING: Using /T on the CONFIG.SYS SHELL= line may lock up Windows 9x / ME GUI upon shut down! [Windows 95 + MS-DOS 7.00 and above ONLY] |
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BACKUP ALL YOUR DATA TO A SAFE LOCATION (not on your hard drive!) before using FDisk. All data on the hard drive will be destroyed. Use ALL FDISK.EXE command line switches with CAUTION, ONLY from native/real MS-DOS mode. NOT from a Windows DOS box/session prompt, even full screen.
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| FDisk The DOS partitioning tool. | |
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Please NOTC: These command switches are book marked. Just click on the command switch to jump to that section. fdisk [/FPRMT] [FDISK x /PRI:n (/PRIO:n) /EXT:n /LOG:n (/LOGO:n)] [/MBR] [/Q] [/STATUS] [/X] [/ACTOK] [/CMBR x] [/PARTN] [/PRMT] | |
| /FPRMT | Bypasses the FDISK startup screen, but enables interactive FAT16/FAT32 support. This can be used to force FDISK to create FAT32 partitions smaller than 512 MB, normally not possible by default.
[Windows 95B OSR 2.0 + MS-DOS 7.10 and above ONLY] |
| FDISK x /PRI:n (or /PRIO:n) /EXT:n /LOG:n (or /LOGO:n) MUST be used together for proper operation.
[MS-DOS 6.00 and above ONLY] Meanings: | |
| x | Drive number: 1, 2, 3... etc. Drive 1 corresponds to the 1st hard disk installed (C), drive 2 to second hard disk (D)... etc. |
| /PRI:n | Creates a primary partition of size n (in MegaBytes) and makes it bootable (active). |
| /PRIO:n | Creates a primary partition of size n (in MegaBytes) and makes it bootable (active) while overriding FAT16/FAT32. |
| /EXT:n | Creates an extended partition of size n (in MegaBytes) which holds logical partition(s). |
| /LOG:n | Creates a logical drive in the extended partition of size n (in MegaBytes). |
| /LOGO:n | Creates a logical drive in the extended partition of size n (in MegaBytes) while overriding FAT16/FAT32. If using FAT16 maximum size allowed is 2,047 MB (2 GigaBytes). If using FAT32 maximum size allowed is 2,047 GB (2 TeraBytes). NOTES: Maximum partition size MUST be equal to or smaller than existing free disk space. /EXT:n and /LOG:n (or /LOGO:n) partition sizes MUST be identical. Only one FDISK "LOG" is allowed per EACH logical drive! Therefore on computers with more than one logical drive you MUST run a separate FDISK x /LOG:n (or /LOGO:n) command for EACH installed drive. ONLY IF using Windows 95B OSR 2.0 + MS-DOS 7.10 or newer: /PRI:n and /LOG:n default to FAT32 on partitions larger than 512 MB, or to FAT16 on partitions smaller than 512 MB. /PRIO:n and /LOGO:n default to FAT16 even on partitions larger than 512 MB, same as older MS-DOS 5.00/6.xx FDISK. ONLY Windows 95 B/C OSR 2.0 - 2.5, 98, 98 SE, 2000, ME, XP and .Net support FAT32. Use /LOGO:n instead of /LOG:n and/or /PRIO:n instead of /PRI:n to ignore FAT information in case of disk access errors. |
| /MBR | Recreates the boot sector of the first (bootable) hard disk overwriting it with a fresh copy, by writing a new Master Boot Record (MBR) based on existent disk structure, without altering the partition table information. It can be used to repair a damaged/corrupted MBR (i.e. by a virus) but you must read the warnings below. FDISK /MBR Rewrites the Master Boot Record The MS-DOS Fdisk utility usually updates the master boot record only if no master boot record exists. Repartitioning with Fdisk does not rewrite this information. [MS-DOS 6.00 and above ONLY] |
| WARNINGS: 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 and disks with more than four partitions. This option should NOT be used if any of the following conditions exist:
Some dual-boot programs have a special MBR that asks you at startup which operating system you want to use. FDISK /MBR erases this program. Dual-boot systems that boot whichever partition is marked Active are not affected by FDISK /MBR | |
| More Information About The MBR: | |
What is the MBR? At the end of the ROM BIOS bootstrap routine, the BIOS reads and executes the first physical sector of the first floppy or hard disk 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 writes this program to the disk only if there is no master boot record. Why is the MBR Changed During Setup? The MS-DOS 5.0 Setup was not completed. 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 version of MS-DOS, UNINSTALL should also remove this message. However, if Setup or UNINSTALL fails to remove this message, or if the master boot record becomes corrupted, a new master boot record can be written to the disk using the following command: C:\>FDISK /MBR | |
| /Q | Prevents rebooting the computer automatically after altering the partition information by using FDISK with other parameters.
[MS-DOS 6.00 and above ONLY] |
| /STATUS | Displays a screen similar to using FDISK's option 4: "Partition information", but shows also extended partition information (if any).
[MS-DOS 5.00 and above ONLY] |
| /X | Limits disk access to a total of 8.4 GB even on larger physical drives, even if the BIOS supports INT13h extensions for hard disks over 8.4 GB, thus preventing the use of 0E and 0F partition types, by ignoring LBA (Logical Block Addressing) and extended disk information. This makes possible disk partitioning on computers with older BIOSes without support for hard disks larger than 8.4 GB. Use /X to start FDISK if you receive disk access, stack overflow and/or data corruption error messages.
[Windows 95 + MS-DOS 7.00 and above ONLY] |
| /ACTOK | Skips disk integrity checking, thus speeding up the partitioning process.
[Windows 95B OSR 2.0 + MS-DOS 7.10 and above ONLY] |
| /CMBR x | /CMBR x MUST be used together for proper operation. Recreates the boot sector of the second, third... etc hard disk(s) (if any) overwriting it (them) with a fresh copy, by writing a new Master Boot Record (MBR) based on existent disk structure, without altering the partition table information. Valid values for x are;
Can be used to repair a damaged/corrupted MBR (i.e. by a virus). [MS-DOS 6.00 and above ONLY] |
| /PARTN | Saves the partition information to a plain text file called PARTSAV.FIL, which can be viewed afterwards using any text editor/viewer, like EDIT.COM in DOS or Notepad in Windows.
[MS-DOS 6.00 and above ONLY] |
| /PRMT | adds extra prompt ["nag"] screens which require user input (key press) before proceeding further.
[MS-DOS 6.00 and above ONLY] |
WARNINGS: | Format The disk formatting utility. | |
| Please NOTC: These command switches are book marked. Just click on the command switch to jump to that section. format [drivC:] [/AUTOTEST] [/BACKUP] [/SELECT] [/U] [/SELECT /U] [/Z:n] | |
| /AUTOTEST | Checks the existing format of your disk, unless the /U (UNCONDITIONAL parameter is also used [MS-DOS 5.00 and above ONLY], and then proceeds with an UNATTENDED DISK(ETTE) FORMAT:
DOES NOT prompt for a volume label! Use CAUTION: This works on BOTH hard and floppy drives! [MS-DOS 5.00 and above ONLY] |
| /BACKUP | Works exactly like /AUTOTEST, applies ONLY to floppy diskettes, but it DOES prompt the user for a volume label, and it DOES display disk space information upon completion.
[MS-DOS 5.00 and above ONLY] |
| /SELECT | Similar to using the MIRROR command [a MS-DOS 5.00 and earlier ONLY utility, removed from all MS-DOS releases beginning with 6.00], and reads the disk(ette) system area (sector 0). In MS-DOS 4.0 FORMAT /SELECT has the same effect as FORMAT /BACKUP.
[MS-DOS 5.00 and above ONLY] |
| /U | Performs an UNCONDITIONAL format, which DESTROYS every byte of data on ANY hard disk/floppy by overwriting it with zeroes (hex F6h). CAUTION: ANY disk(ette) formatted using /U can NOT be UNFORMATTED! [MS-DOS 5.00 and above ONLY] |
| /SELECT /U | NEVER use these two FORMAT switches TOGETHER on ANY drive! The drive WILL become unusable. FORMAT [drivC:] /SELECT /U makes a disk(ette) UNREADABLE by filling the system area (sector 0) with zeroes (hex F6h), due to using these two incompatible options together. All other sectors are left intact. [MS-DOS 5.00 and above ONLY] |
| /Z:n | Formats a FAT32 drive with a cluster size of n times 512 Bytes. Meanings: [drivC:] = your hard drive letter: C:, D:, C:... etc. Examples: n = 1 creates a cluster of 512 Bytes CAUTION: It's recommended that you do not change the default cluster size. Some programs such as disk-repair or anti-virus tools may STOP working properly if you do! [Windows 95B OSR 2.0 + MS-DOS 7.10 and above ONLY] |
| Scandisk disk repair program | |
| To check and repair a drive, use the following syntax
SCANDISK [drivC: | drivC:\DRVSPACE.nnn] | |
| DrivC: | Drive to check |
| drivC:\DRVSPACE.nnn | The unmounted drivespace drive to check. This is the only way to check an unmounted drivespace in Windows. |
| None | Checks and repair the current drive |
| /All | Checks and repairs all local drives. |
| /Autofix | Fixes damage without prompting. |
| /Checkonly | Checks a drive, but does not repair any damage. |
| /Custom | Configures and runs ScanDisk according to SCANDISK.INI settings. |
| /Nosave | With /AUTOFIX, deletes lost clusters rather than saving as files. |
| /Nosummary | With /CHECKONLY or /AUTOFIX, prevents ScanDisk from stopping at summary screens. |
| /Surface | Performs a surface scan after other checks. |
| /Mono | Configures ScanDisk for use with a monochrome display. |
| /Fragment [drivC:][path] filename | Examine a file for fragmentation: Works in Windows |
| /Undo [drivC:] | To undo repairs you made previously. Where [drivC:], specifes the drive containing your Undo disk. |
| /Time | Monitor the average read, write, and seek times during surface analysis. This detects sectors that are about to go bad but can still be read. This is the same as ScanTimeOuts in scandisk.ini. |
| /Text | Runs Scandisk as a MS-Dos prompt command. Can check but not fix problems. |
| /Help | Displays command line help. |
| /Noui | |
| /Clip | |
| /Nolost | |
| /Mount | |
| /New | |
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| 0 | Never |
| 1 | After prompting |
| 2 | Always. |
| Scandisk.Ini |
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See Scandisk.ini in the Windows\Command directory for customizing how Scandisk runs when started with the /custom switch. This is a fully commented file. Click here for your Scandisk.ini (assumes you've installed Windows to C:\Windows |
| Scanreg the windows registry tool | |
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Backs up, restores, and repairs the Windows registry from the DOS command prompt. | |
| scanreg [/Dir] [/Backup] [/Nop] [/Opt] [/Autorun] [/Restore] [/Help] [/?] [/Comment] [/Win][/Fix] | |
| <nothing> | Checks the registry and asks do you want to back it up. |
| RegistryFile | The registry file to check. |
| /Dir | Shows a UI with a test and cancel button. |
| /Backup | Backs up the registry |
| /Nop | Shows a UI without user input. |
| /Opt | Optimises the registry by compacting it |
| /Autorun | Windows Registry Checker automatically scans the system registry for invalid entries and empty data blocks when it is started. If invalid registry entries are detected, Windows Registry Checker automatically restores a previous day's backup. This is equivalent to running "scanreg /autorun" (without quotation marks) from a command prompt. If no backups are available, Windows Registry checker tries to make repairs to the registry. This is equivalent to running "scanreg /fix" (without quotation marks) from a command prompt. If the registry contains more than 500K of empty data blocks, Windows registry Checker automatically optimizes it. |
| /Restore | Restores previously backed up |
| /Help | Shows a subset of the command line switches |
| /? | Shows a subset of the command line switches |
| "/Comment=Text" | Adds a comment to a backup. This doesn't cause a backup to be created, but if one is created by another command line switch or the user choosing to backup then this comment will be added. |
| /Win |
(from David Candy) Shows a UI, tests the registry and shows options to backup or restore the registry. |
| /Fix | Repairs the registry and compacts the registry by completely rebuilding it. |
| Ver Retrieves the OS version information. | |
| ver [/r] This is the only switch available for the ver command | |
| None | Retrieves the standard version information. Example of screen output for plain VER command (using Win98 SE + MS-DOS 7.10) Windows 98 [Version 4.10.2222] |
| /r | (REVISION) displays extended DOS info: the DOS revision and the memory location of the DOS module, in addition to using the plain VER command. Example of screen output for VER /R command (using Win98 SE + MS-DOS 7.10):
Windows 98 [Version 4.10.2222] [MS-DOS 5.00 and above ONLY] |
| Win (Win.com) The Windows startup command. (Windows 95 and 98 versions only) | |
| WIN [/W] [/WX] [/Z] | |
| NOTC: Microsoft removed ALL WIN.COM undocumented switches detailed below from Windows ME and onwards! | |
| /W | Generates the following messagC:
Press any key to continue... Pressing a key reboots the system back to Windows 95 (98). DOS=SINGLE which does NOT allow Windows 95/98 GUI to load. |
| /WX | Automatically restarts the computer (warm reboot), without prompting or waiting for input (key press), and restores the original CONFIG.SYS and AUTOEXEC.BAT files in the root directory of the boot drive from CONFIG.WOS and AUTOEXEC.WOS (if any). This is useful when the computer is restarted after interrupting a "single" mode MS-DOS session, because of this CONFIG.SYS linC: DOS=SINGLE which does NOT allow Windows 95/98 GUI to load. [Windows 95 and above ONLY] |
| /Z | Automatically forces the ATX power supply to (soft-)power off the computer ONLY on ATX motherboards, without prompting or waiting for input (key press). This switch works ONLY if executed from the native/real/true MS-DOS mode OUTSIDE the Windows GUI, NOT from WITHIN Windows in a DOS prompt/box/session. [Windows 95B OSR 2.1 and above ONLY] |
| Winipcfg | |
| Winipcfg is a DOS utility which can be used from MS-DOS or a MS-DOS shell (including Windows) to display the network settings currently assigned and given by a network. This command can be utilized to verify a network connection as well as to verify your network settings. | |
| Winipcfg [/all] [/batch (file)] [/renew_all] [/release_all] [/renew n] [/release n] | |
| nothing | Starts with a User dialog to set the IP configuration. |
| /all | Display detailed information - you get a button you can click without using this. |
| /batch (file) | Write to file or /winipcfg.out |
| /renew_all | Renew all adapters |
| /release_all | Release all Adapters |
| /renew n | Renew adapter n |
| /release n | Release Adapter n |
