On Sun, Feb 21, 2021 at 6:15 PM Jim Hall <[email protected]> wrote:

> On the virtual get-together today, we tested the new FDISK 1.3.3 with a
> large virtual hard disk. I wanted to report a bug from that.
>
> Test setup: QEMU on Linux. "hda" (hard drive .. created with *qemu-img
> create 4gb.img 4G*) is set to a blank 4GB virtual disk file. "fda"
> (floppy) is set to a virtual floppy image with a copy of FDISK 1.3.3.
> "cdrom" is set to FreeDOS 1.3 RC3 (basically, the initial boot environment)
>
> Procedure: Boot QEMU using FreeDOS 1.3 RC3 and go into the installer, but
> immediately exit to DOS. This means the FreeDOS installer is on "A:" and
> the floppy image with FDISK 1.3.3 is on "B:"
> [...]
> Interestingly, things are quite different if I don't try to create that
> last 8MB logical drive. I'll send that in a follow-up.
>


Starting again with a completely new virtual hard drive image.

Same process: boot into the installer, but immediately exit to DOS. Run
FDISK 1.3.3 (and yes, I said "Y" to "Do you want to use large disk (FAT32)
support")

1. "Create DOS partition or Logical DOS Drive" - "Create Primary DOS
Partition" - FDISK shows "Maximum space available for partition is 4103
Mbytes" but I created the partition as only "3000" Mbytes.

... this creates a "3004" Mbytes partition

2. "Create DOS partition or Logical DOS Drive" - "Create Extended DOS
Partition" - FDISK shows "Maximum space available for partition is 1098
Mbytes" and I used that default value to create the extended partition

... this creates a "1090" extended partition

3. FDISK lets me immediately set up a logical drive in the extended
partition. Set the first partition to "500" Mbytes

... this creates a "502" Mbytes partition

4. FDISK lets me immediately set up another logical drive. The "Maximum
space available for partition is 596 Mbytes" so I set the second partition
to that default value of "596" Mbytes

... this creates a "588" Mbytes partition

5. FDISK lets me immediately set up another logical drive - but in this
case, I back out to the main FDISK menu (but don't exit FDISK)

6. "Create DOS partition or Logical DOS Drive" - "Create Logical DOS
Drive(s) in the Extended DOS Partition" and I can see the "D:" logical
drive is "502 Mbytes" and the "E:" logical drive is "588 Mbytes" - and
FDISK says "All available space in the Extended DOS Partition is assigned
to logical drives"

... I am unable to create new partitions now (which is correct because
there's no more free space)


And that leaves me with a usable hard drive.

If I shut down QEMU, and use Linux fdisk to examine the virtual drive
image, I see this:

$ fdisk -l 4gb.img
> Disk 4gb.img: 4 GiB, 4294967296 bytes, 8388608 sectors
> Units: sectors of 1 * 512 = 512 bytes
> Sector size (logical/physical): 512 bytes / 512 bytes
> I/O size (minimum/optimal): 512 bytes / 512 bytes
> Disklabel type: dos
> Disk identifier: 0x00000000
> Device     Boot   Start     End Sectors   Size Id Type
> 4gb.img1             63 6152894 6152832   2.9G  b W95 FAT32
> 4gb.img2        6152895 8385929 2233035   1.1G  5 Extended
> 4gb.img5        6152958 7181054 1028097   502M  6 FAT16
> 4gb.img6        7181118 8385929 1204812 588.3M  b W95 FAT32



There's some wasted space here, but it's a perfectly valid partition table.


So it seems there's a problem in FDISK when creating partitions. It's not
calculating available space correctly.



Jim
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