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Backs up one or more files from one disk onto another.

You can back up files onto either a hard disk or floppy disk(s). Files can also be backed up from one floppy disk onto another, even if the disks have different numbers of sides or sectors. Windows NT displays the name of each file it backs up.

backup source destination-drive: [/s] [/m] [/a][/f[:size]] [/d:date [/t:time]][/l[:[drive:][path]logfile]]



Specifies the location of files you want to back up. Source can consist of a drive letter and colon, a directory name, a filename, or a combination.


Specifies the drive that contains the disk on which you wantUto store any backup files. The backup files are stored in the BACKUP.nnn and CONTROL.nnn files. That is, backup assigns the names BACKUP.001 and CONTROL.001 to the files it creates on the first backup disk you use, BACKUP.002 and CONTROL.002 to the files it creates on the second backup disk, and so on.


Backs up the contents of all subdirectories.


Backs up only files that have changed since the last backup, and turns off the archive attribute of the original files.


Adds backup files to an existing backup disk without deleting existing files. (The /a switch is ignored if the existing backup disk contains backup files that were created by using the backup command from MS-DOS version 3.2 or earlier.)


Formats the backup disk to the size you specify. (The format command must be present in the current path.) With this switch, you direct backup to format floppy disks that do not match the default size of the drive. The backup command formats an unformatted destination disk even if you do not specify the /f switch. When backup finishes formatting, it begins backing up files onto the last disk it formatted. Size specifies the size in kilobytes of the disk to be formatted. If you do not specify size, the /f switch uses the default size of the drive. The following list shows the valid values for size and a brief description of each size:

160 or 160k or 160kb 160K, single-sided, double-density, 5.25-inch disk

180 or 180k or 180kb 180K, single-sided, double-density, 5.25-inch disk

320 or 320k or 320kb 320K, double-sided, double-density, 5.25-inch disk

360 or 360k or 360kb 360K, double-sided, double-density, 5.25-inch disk

720 or 720k or 720kb 720K, double-sided, double-density, 3.5-inch disk

1200 or 1200k or 1200kb or 1.2 or 1.2m or 1.2mb 1.2-MB, double-sided, quadruple-density, 5.25-inch disk

1440 or 1440k or 1440kb or 1.44 or 1.44m or 1.44mb 1.44-MB, double-sided, quadruple-density, 3.5-inch disk

2880 or 2880k or 2880kb or 2.88 or 2.88m or 2.88mb 2.88-MB, double-sided, 3.5-inch disk


Backs up only files modified on or after the specified date. The date format depends on the setting you are using for the country command.


Backs up only files modified at or after the specified time. The time format depends on the setting you are using for the country command.


Creates a log file and adds an entry to that file to record the backup operation. If you do not specify a location for the log file, backup puts the file in the root directory of the source drive. If you do not specify logfile, backup names the file BACKUP.LOG. You should not specify a removable drive (such as a floppy disk drive) for this parameter; but once the backup is complete, you can copy the log file to a floppy disk.

More Information About Backup

ntcmds00000001.gif Backup--Notes

ntcmds00000001.gif Backup--Examples


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