DISK PARTITIONS


ST-DOS uses its own disk partitioning scheme. Currently ST-DOS also supports
MS-DOS partitions, but with large disks it is recommended to use ST-DOS's own
partitioning system, because it allows an unlimited number of partitions.
The SETUP.COM program can automatically fill the disk with 2 GB partitions.


  Partitioning the disk manually

The RFSDRV.EXE filesystem driver must be loaded first. 

If the disk is already partitioned and you want to modify the existing
partitions, RFSDRV needs the disk number as a command line argument. The
"partition table" of that drive is then mounted as a filesystem.

If the disk is not partitioned yet, RFSDRV must be loaded without arguments.
If the computer does not have floppy disks, the first hard disk drive is 0.
If the computer has 1 or 2 floppy disks, the first hard disk drive is 2. If
the computer has 3 or 4 hard disks, the first hard disk drive is 4.

After loading the RFSDRV driver you can run MKPARTS.COM to create partitions.
MKPARTS needs the disk number of the target drive as a command line argument.

First MKPARTS wants to know how large partition system you want to create.
Usually you want to fill the entire disk with the partition table, so the
default option is good.

Then it's time to create the partitions. If you press [A], MKPARTS fills the
disk automatically with 2 GB partitions and makes the first partition
bootable. By pressing [I] you can manually define the size of each partition
and select which partition becomes bootable. Note that the boot code doesn't
currently support booting from partitions that begin from beyond the 8,4 GB
threshold.

MKPARTS calls FORMAT.COM automatically with correct arguments based on the
disk geometry and partition size, and a FAT16 filesystem is created. You can
later overwrite the FAT filesystem with something else, if you want to do so.


  Modifying existing partitions

When RFSDRV is ran with the disk number as a command line argument, it mounts
the partition system to the first free mountpoint as a filesystem. In that
filesystem you can browse, add, edit and delete the existing partitions and
other files in the partition system.

Two special file attributes control whether the file is a partition and
bootable. The P attribute makes the file a partition and the B attribute
makes it bootable. The bootloader searches the partition system for the first
file that has the B attribute set and then boots it. The attributes can be
set using the ATTRIB command - for example, the following command makes
MYPART.IMG a partition:

ATTRIB +P MYPART.IMG

Note that the first bootable entry does not need to be an actual filesystem.
It can be anything, for example a boot sector demo - the P attribute does not
need to be set for the bootable entry. The bootloader only looks for the B
attribute and the partition mounter looks for the P attribute.

Because the system has only a limited number of mountpoints, you may
sometimes have to disable the partition status for some entries to make room
in the mountpoints for another.



  Using the partition system to store large files

The "partition table" is in fact a simple filesystem where each file is
stored on the disk contiguously so that the kernel can mount them as a
partition. This means that the partition table can also be used for storing
large files. Currently the maximum size of actual files is 4 GB, so that is
also the size limit of the files stored in the partition table.

Currently the allocator of the RFSDRV driver is very stupid and it always
starts the new file from the first free block from the beginning, so it
very easily gets into a situation where it can only create a small file and
an attempt to grow the file larger ends up in a "disk full" error. A defrag
program must be made to fix this.