A user may also load a specific version of DOS or another 8086 operating system into a VMB session from a diskette image stored on the hard disk. This is achieved by specifying the fully qualified filename of the diskette image file as the value for DOS_STARTUP_DRIVE under DOS Settings.
Here is an example using the DOS 5 boot diskette created in the Booting from Diskette above:
E:\OS2\MDOS\FSACCESS G: = A:
Images may be created using the VMDISK utility supplied with OS/2 Version 2.0. The syntax of the VMDISK command is:
vmdisk <source drive> <image filename>
For example:
VMDISK a: c:\bootimg\dos50.vmb
The image file is a complete binary "dump" of the diskette, consisting of a short header record followed by the diskette's boot sector, FAT(s), and all data clusters. Its file size corresponds to the size of the source diskette, regardless of the amount of space actually used on the source diskette. No compression of the image is performed.
The diskette must have a standard DOS format (FAT, 512 byte sectors). It is not possible to create, then boot, an image of a copy-protected diskette which has a non-DOS format. It may be possible to boot such a diskette directly in a VDM.
The VMDISK utility can run under either DOS or OS/2, and supports all 3½ inch (720KB, 1.44MB and 2.88MB) and 5¼ inch (360KB and 1.2MB) source diskette formats.
Note that VMDISK works one way only; it is not possible to create a diskette from a VMDISK image.