DR-DOS/Caldera-OpenDOS-7.01 floppy images not recognized

[Frank Batschulat (Oracle)]

Trying to install DR-DOS 7/Caldera OpenDOS 7 fails because we cannot recognize the floppy images:

if you grab them from:

​https://winworldpc.com/product/dr-dos/7x

We fail with the following error during the attempt to boot from the floppy initally:

Failed to open the disk image file /home/sw/Caldera-OpenDOS-7.01/Full-1440/DISK01.IMG.
 
GUI-error:
 
Could not get the storage format of the medium '/home/sw/Caldera-OpenDOS-7.01/Full-1440/DISK01.IMG' (VERR_NOT_SUPPORTED).
 
Result Code: VBOX_E_IPRT_ERROR (0x80BB0005)
Component: MediumWrap
Interface: IMedium {ad47ad09-787b-44ab-b343-a082a3f2dfb1}
Callee: IVirtualBox {d0a0163f-e254-4e5b-a1f2-011cf991c38d}
Callee RC: VBOX_E_OBJECT_NOT_FOUND (0x80BB0001)
 
Logfile: VBoxSVC.log
 
09:00:56.107381 nspr-9   ERROR [COM]: aRC=VBOX_E_IPRT_ERROR (0x80bb0005) aIID={ad47ad09-787b-44ab-b343-a082a3f2dfb1} aComponent={MediumWrap} aText={Could not get the storage format of the medium '/home/sw/Caldera-OpenDOS-7.01/Full-1440/DISK01.IMG' (VERR_NOT_SUPPORTED)}, preserve=false aResultDetail=-37

We get the following information for the floppy images:

$ pwd
/home/sw/Caldera-OpenDOS-7.01/Full-1440
VBox/6.0 fbatschu@lserver Full-1440 $ file *
DISK01.IMG: DOS/MBR boot sector, code offset 0x56+2, OEM-ID "OPENDOS7", root entries 224, sectors 2880 (volumes <=32 MB), sectors/FAT 9, sectors/track 18, serial number 0x18e44553, label: "DISK_01    ", FAT (12 bit), followed by FAT
DISK02.IMG: DOS/MBR boot sector, code offset 0x56+2, OEM-ID "OPENDOS7", root entries 224, sectors 2880 (volumes <=32 MB), sectors/FAT 9, sectors/track 18, serial number 0x18e50c23, unlabeled, FAT (12 bit), followed by FAT
DISK03.IMG: DOS/MBR boot sector, code offset 0x56+2, OEM-ID "OPENDOS7", root entries 224, sectors 2880 (volumes <=32 MB), sectors/FAT 9, sectors/track 18, serial number 0x18e50e5d, unlabeled, FAT (12 bit), followed by FAT
DISK04.IMG: DOS/MBR boot sector, code offset 0x56+2, OEM-ID "OPENDOS7", root entries 224, sectors 2880 (volumes <=32 MB), sectors/FAT 9, sectors/track 18, serial number 0x18e51139, unlabeled, FAT (12 bit), followed by FAT
DISK05.IMG: DOS/MBR boot sector, code offset 0x56+2, OEM-ID "OPENDOS7", root entries 224, sectors 2880 (volumes <=32 MB), sectors/FAT 9, sectors/track 18, serial number 0x18e51457, unlabeled, FAT (12 bit), followed by FAT

interestingly, grabbing the floppy images for PC-DOS 2000 and do an instalation with them, works fine, those images from:

​https://winworldpc.com/product/pc-dos/2000

those working images look like this:

/home/sw/isos/IBM-PC-DOS-2000$ file disk*
disk01.img: DOS/MBR boot sector, code offset 0x3c+2, OEM-ID "IBM  7.0", root entries 224, sectors 2880 (volumes <=32 MB), sectors/FAT 9, sectors/track 18, serial number 0x226f11d4, label: "DISK      1", FAT (12 bit), followed by FAT
disk02.img: DOS/MBR boot sector, code offset 0x3c+2, OEM-ID "IBM  7.0", root entries 224, sectors 2880 (volumes <=32 MB), sectors/FAT 9, sectors/track 18, serial number 0x1e3d10db, label: "DISK      2", FAT (12 bit), followed by FAT
disk03.img: DOS/MBR boot sector, code offset 0x3c+2, OEM-ID "IBM  7.0", root entries 224, sectors 2880 (volumes <=32 MB), sectors/FAT 9, sectors/track 18, serial number 0xb5910dd, label: "DISK      3", FAT (12 bit), followed by FAT
disk04.img: DOS/MBR boot sector, code offset 0x3c+2, OEM-ID "IBM  7.0", root entries 224, sectors 2880 (volumes <=32 MB), sectors/FAT 9, sectors/track 18, serial number 0x395a10de, label: "DISK      4", FAT (12 bit), followed by FAT
disk05.img: DOS/MBR boot sector, code offset 0x3c+2, OEM-ID "IBM  7.0", root entries 224, sectors 2880 (volumes <=32 MB), sectors/FAT 9, sectors/track 18, serial number 0x332010e0, label: "DISK      5", FAT (12 bit), followed by FAT
disk06.img: DOS/MBR boot sector, code offset 0x3c+2, OEM-ID "IBM  7.0", root entries 224, sectors 2880 (volumes <=32 MB), sectors/FAT 9, sectors/track 18, serial number 0x314f10e2, label: "DISK      6", FAT (12 bit), followed by FAT