PXE DOS

cd /tftpboot/
cp -pi /usr/share/syslinux/memdisk ./

MSDOS

mkdir -p /tftpboot/msdos/
cd /tftpboot/msdos/
wget https://lab.nethence.com/elge/floppy/win98sc.img
wget https://lab.nethence.com/elge/floppy/dos622.img

vi /tftpboot/pxelinux.cfg/default

label msdos622
    kernel memdisk
    initrd msdos/dos622.img

label msdos98sc
    kernel memdisk
    initrd msdos/win98sc.img

CUSTOM MSDOS FAT12 2.88M FLOPPY

tested, works

    dd if=/dev/zero of=floppy288.img bs=1024 count=2880
    mkfs.fat -F 12 floppy288.img
    ms-sys --fat12 --force floppy288.img
    mount -o loop floppy288.img /mnt/

    cp lala/MSDOS.SYS /mnt/
    cp lala/IO.SYS /mnt/
    cp lala/COMMAND.COM /mnt/
    #cp lala/CONFIG.SYS /mnt
    #cp lala/AUTOEXEC.BAT /mnt

    umount /mnt

FREEDOS

mkdir -p /tftpboot/freedos/
cd /tftpboot/freedos/

wget http://www.freedos.org/download/download/FD12FLOPPY.zip
unzip FD12FLOPPY.zip
chmod -x FLOPPY.img

wget http://www.ibiblio.org/pub/micro/pc-stuff/freedos/files/distributions/1.3/previews/1.3-rc1/FD13-Floppy.zip
unzip FD13-Floppy.zip

label freedos12
    kernel memdisk
    initrd freedos/FLOPPY.img

label freedos13
    kernel memdisk
    initrd freedos/FD13FLOP.IMG

CUSTOM FREEDOS FAT16 MEMSTICK

assuming a custom freedos image is ready

label freedos/fw
    kernel memdisk
    initrd freedos/FDSTD10.IMG
    append harddisk c=19 h=16 s=63

RESOURCES

Floppy images http://www.syslinux.org/wiki/index.php?title=MEMDISK#Floppy_images

Booting FreeDOS via PXE https://possiblelossofprecision.net/?p=491

MEMDISK https://wiki.syslinux.org/wiki/index.php?title=MEMDISK

Create a Custom Sized FreeDOS Boot Image (and how to PXE boot it) https://www.tyler-wright.com/create-a-custom-sized-freedos-boot-image-and-how-to-pxe-boot-it/