Backup--Notes

Backing up onto a disk with files

Unless you use the /a switch, backup deletes old files (including read-only files) from a backup disk before adding new files to it.

Backup log file

If you use the /l switch and do not specify a name and location for the log file, the backup command adds a file named BACKUP.LOG to the root directory of the source drive. If the BACKUP.LOG file already exists, backup adds the current entry to the file. A backup log-file entry uses the following format:

The date and time of the backup appear on the first line.

Each filename appears on a separate line with the number of the backup disk that contains the file.

The backup log file can assist you later, when you need to identify the files you want to restore. The restore command always returns a file to the original directory or subdirectory recorded in the backup log, creating the subdirectory if necessary.

Labeling backup disks

It is important to label and number backup disks consecutively. As each disk is filled, backup prompts you for the next disk. When you restore files, you need to insert the backup disks into the disk drive in the same sequence. To check the sequence of backup disks (MS-DOS version 3.3 or later), use the dir command to check the disk number.

Backup and system files

The backup command cannot back up the system files IO.SYS, MSDOS.SYS, and CMD.EXE. You can use the sys command to copy these files onto a floppy disk.

Using an old version of the restore command

You cannot use an old version of the restore command (MS-DOS version 3.2 or earlier) for files backed up with MS-DOS version 3.3 or later. If you attempt this, Windows NT displays the following message:

Source does not contain backup files

This error occurs because the format of old backup files differs from the format of files backed up with MS-DOS versions 3.3 and later.

Backup exit codes

The following list shows each exit code and given a brief description of its meaning:

0	The backup was successful.
1	No files were found to back up.
2	Some files were not backed up because of file-sharing conflicts.
3	The user pressed CTRL+C to stop the process.
4	The process stopped because of an error.

You can use the errorlevel parameter on the if command line in a batch program to process exit codes returned by the backup command. For an example of a batch program that processes exit codes, see Backup--Examples.

More Information About Backup

Backup--Examples

Backup