BACKUP (MS-DOS)
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{{FormatInfo | {{FormatInfo | ||
| − | |subcat= | + | |subcat=Backup |
| − | |extensions={{ext|@@@}}, others | + | |extensions={{ext|@@@}}, {{ext|@01}}, {{ext|001}}, others |
}} | }} | ||
| − | + | Some versions of [[MS-DOS]] have a '''BACKUP''' command, whose main use is to back up some or all of the contents of a hard disk to a set of floppy disks. The '''RESTORE''' command is used to restore files. The backup format was undocumented. | |
| − | The | + | There are at least two quite different formats: |
| + | * The format used by MS-DOS 2.0(?) through 3.2. We'll call it 2.0 format. | ||
| + | * The format used by MS-DOS 3.3 through 5.x. We'll call it 3.3 format. | ||
| + | |||
| + | For the format used by MS-DOS 6.x's MSBACKUP.EXE utility, see [[Norton Backup]]. | ||
| + | |||
| + | == Format details == | ||
| + | === Format details - 2.0 === | ||
| + | Backed up files usually keep their original filenames. The data is modified, at least to add a header. In case of a duplicate filename (because the same filename appeared in different directories), a replacement extension like '''.@01''' or '''.@02''' is evidently used. A file may be split into multiple backup files, each containing a fragment of the original data. | ||
| + | |||
| + | An extra BACKUPID.@@@ file is written to each disk, containing general information about the backup. It doesn't contain any critical information. | ||
| + | |||
| + | === Format details - 3.3 === | ||
| + | Just two files are written to each floppy disk: CONTROL.001 (or .002, etc.), and BACKUP.001 (.002, etc.). The CONTROL file contains information about the file data in the corresponding BACKUP file. | ||
| + | |||
| + | == Identification == | ||
| + | === Identification - 2.0 === | ||
| + | BACKUPID.@@@: The first byte of the file is either {{magic|0xff}} or {{magic|0x00}}. The file is exactly 128 bytes in size. (TODO: More info) | ||
| + | |||
| + | Data files: It's possible to heuristically identify data files from their contents, but they don't really have any distinctive markings. The first byte of a file is either {{magic|0xff}} or {{magic|0x00}}. Non-fragmented archives start with bytes {{magic|ff 01 00}}. (TODO: More info) | ||
| + | |||
| + | === Identification - 3.3 === | ||
| + | A CONTROL.* file starts with byte {{magic|0x8b}}, followed by ASCII "{{magic|BACKUP }}" (which ends with two spaces). | ||
| + | |||
| + | The BACKUP.* files can't be identified from their contents, as they contain nothing other than the contents of the backed up files. | ||
| + | |||
| + | == Specifications == | ||
| + | * [https://www.ibiblio.org/pub/micro/pc-stuff/freedos/files/dos/restore/brtecdoc.htm Tech docs from FreeDOS] | ||
| + | * One could presumably learn about at least one of the formats from the MS-DOS 4.0 source code, listed below. | ||
| + | |||
| + | == Software == | ||
| + | * [https://winworldpc.com/product/ms-dos/3x MS-DOS], at WinWorld | ||
| + | * MS-DOS 4.0 source code: [https://github.com/microsoft/MS-DOS/tree/main/v4.0/src/CMD/BACKUP BACKUP], [https://github.com/microsoft/MS-DOS/tree/main/v4.0/src/CMD/RESTORE RESTORE] | ||
| + | * {{Deark}} | ||
| + | |||
| + | == Sample files == | ||
| + | 2.0 format: | ||
| + | * {{DexvertSamples|archive/dosBackupFile}} | ||
| + | * [{{DiscMasterURL|browse/30126/07.iso/c/c006}}] → *.ddi ([[DDI|DiskDupe]] format) → ... | ||
| + | ** Examples of split files are LNALLMS.BAT from parts 1 and 2, and BTPARSE.EXE from parts 2 and 3. | ||
| + | |||
| + | 3.3 format: | ||
| + | * {{{CdTextfiles|pcblueii/PCBLUE/VOL583.ZIP|VOL583.ZIP}}, {{CdTextfiles|pcblueii/PCBLUE/VOL584.ZIP|VOL584.ZIP}}} → ... | ||
| + | * [{{DiscMasterURL|browse/15395/NSS_Collection.iso/3-103%20might%20and%20magic%20iii%20%20144}}] → *.imz → ... | ||
== Links == | == Links == | ||
| − | |||
* [http://www.computerhope.com/backup.htm Backup command help] | * [http://www.computerhope.com/backup.htm Backup command help] | ||
| + | [[Category:Archiving]] | ||
[[Category:Microsoft]] | [[Category:Microsoft]] | ||
| + | [[Category:MS-DOS]] | ||
| + | [[Category:Multi-file formats]] | ||
[[Category:File formats with too many extensions]] | [[Category:File formats with too many extensions]] | ||
Latest revision as of 12:44, 23 August 2025
Some versions of MS-DOS have a BACKUP command, whose main use is to back up some or all of the contents of a hard disk to a set of floppy disks. The RESTORE command is used to restore files. The backup format was undocumented.
There are at least two quite different formats:
- The format used by MS-DOS 2.0(?) through 3.2. We'll call it 2.0 format.
- The format used by MS-DOS 3.3 through 5.x. We'll call it 3.3 format.
For the format used by MS-DOS 6.x's MSBACKUP.EXE utility, see Norton Backup.
Contents |
[edit] Format details
[edit] Format details - 2.0
Backed up files usually keep their original filenames. The data is modified, at least to add a header. In case of a duplicate filename (because the same filename appeared in different directories), a replacement extension like .@01 or .@02 is evidently used. A file may be split into multiple backup files, each containing a fragment of the original data.
An extra BACKUPID.@@@ file is written to each disk, containing general information about the backup. It doesn't contain any critical information.
[edit] Format details - 3.3
Just two files are written to each floppy disk: CONTROL.001 (or .002, etc.), and BACKUP.001 (.002, etc.). The CONTROL file contains information about the file data in the corresponding BACKUP file.
[edit] Identification
[edit] Identification - 2.0
BACKUPID.@@@: The first byte of the file is either 0xff or 0x00. The file is exactly 128 bytes in size. (TODO: More info)
Data files: It's possible to heuristically identify data files from their contents, but they don't really have any distinctive markings. The first byte of a file is either 0xff or 0x00. Non-fragmented archives start with bytes ff 01 00. (TODO: More info)
[edit] Identification - 3.3
A CONTROL.* file starts with byte 0x8b, followed by ASCII "BACKUP " (which ends with two spaces).
The BACKUP.* files can't be identified from their contents, as they contain nothing other than the contents of the backed up files.
[edit] Specifications
- Tech docs from FreeDOS
- One could presumably learn about at least one of the formats from the MS-DOS 4.0 source code, listed below.
[edit] Software
[edit] Sample files
2.0 format:
- dexvert samples — archive/dosBackupFile
- [1] → *.ddi (DiskDupe format) → ...
- Examples of split files are LNALLMS.BAT from parts 1 and 2, and BTPARSE.EXE from parts 2 and 3.
3.3 format:
- {VOL583.ZIP, VOL584.ZIP} → ...
- [2] → *.imz → ...
