mtools: miscellaneous variables
3.5.5 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 (precmd) or an
integer (all others)
'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 auto-detected number of fat bits wrong, or if
you want to mformat a disk with a weird number of fat bits.
'codepage'
Describes the DOS code page used for short filenames. This is a
number between 1 and 999. By default, code page 850 is used. The
reason for this is because this code page contains most of the
characters that are also available in ISO-Latin-1. You may also
specify a global code page for all drives by using the global
'default_codepage' parameter (outside of any drive description).
This parameters exists starting at version 4.0.0
'data_map'
Remaps data from image file. This is useful for image files which
might need additional zero-filled sectors to be inserted. Such is
the case for instance for IBM 3174 floppy images. These images
represent floppy disks with fewer sectors on their first cylinder.
These missing sectors are not stored in the image, but are still
counted in the filesystem layout. The data_map allows to fake
these missing sectors for the upper layers of mtools. A data_map
is a comma-separated sequence of source type and size. Source type
may be 'zero' for zero-filled sectors created by map, 'skip' for
data in raw image to be ignored (skipped), and nothing for data to
be used as is (copied) from the raw image. Datamap is
automatically complemented by an implicit last element of data to
be used as is from current offset to end of file. Each size is a
number followed by a unit: 's' for a 512 byte sector, 'K' for
Kbytes, 'M' for megabytes, 'G' for gigabytes, and nothing for
single bytes.
Example:
'data_map=1s,zero31s,28s,skip1s' would be a map for use with IBM
3174 floppy images. First sector ('1s', boot sector) is used as
is. Then follow 31 fake zero-filled sectors ('zero31s'), then the
next 28 sectors from image ('28s') are used as is (they contain FAT
and root directory), then one sector from image is skipped
('skip1s'), and finally the rest of image is used as is (implicit)
'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,
independently of the sector size registered in the file system'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 auto-detected value is
used.
Info Catalog
mtools: open flags
mtools: per drive variables
mtools: miscellaneous flags