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(mtools.info)misc variables

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General Purpose Drive Variables
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   The following general purpose drive variables are available.
Depending to their type, these variables can be set to a string (file,
precmd) or an integer (all others)

`file'
     The name of the file or device holding the disk image. This is
     mandatory. The file name should be enclosed in quotes.

`partition'
     Tells mtools to treat the drive as a partitioned device, and to
     use the given partition. Only primary partitions are accessible
     using this method, and they are numbered from 1 to 4. For logical
     partitions, use the more general `offset' variable. The
     `partition' variable is intended for removable media such as
     Syquests, ZIP drives, and magneto-optical disks. Although
     traditional DOS sees Syquests and magneto-optical disks as `giant
     floppy disks' which are unpartitioned, OS/2 and Windows NT treat
     them like hard disks, i.e. partioned devices. The `partition' flag
     is also useful DOSEMU hdimages. It is not recommended for hard
     disks for which direct access to partitions is available through
     mounting.

`offset'
     Describes where in the file the MS-DOS filesystem starts. This is
     useful for logical partitions in DOSEMU hdimages, and for ATARI
     ram disks. By default, this is zero, meaning that the filesystem
     starts right at the beginning of the device or file.

`fat_bits'
     The number of FAT bits. This may be 12 or 16. This is very rarely
     needed, as it can almost always be deduced from information in the
     boot sector. On the contrary, describing the number of fat bits may
     actually be harmful if you get it wrong. You should only use it if
     mtools gets the autodetected number of fat bits wrong, or if you
     want to mformat a disk with a weird number of fat bits.

`precmd'
     On some variants of Solaris, it is necessary to call 'volcheck -v'
     before opening a floppy device, in order for the system to notice
     that there is indeed a disk in the drive. `precmd="volcheck -v"'
     in the drive clause establishes the desired behavior.

`blocksize'
     This parameter represents a default block size to be always used
     on this device.  All I/O is done with multiples of this block size,
     independantly of the sector size registered in the filesystem's
     boot sector.  This is useful for character devices whose sector
     size is not 512, such as for example CD Rom drives on Solaris.

   Only the `file' variable is mandatory. The other parameters may be
left out. In that case a default value or an autodetected value is used.