# use fdisk to create partition
root@cpfong-1018P:/home/cpfong/tmp/trash/syslinux-603/bios/linux# fdisk -l /dev/sdb
Device     Boot Start    End Sectors  Size Id Type
/dev/sdb1        2048 206847  204800  100M  b W95 FAT32

# copy file to /dev/sdb1
root@cpfong-1018P:/home/cpfong/tmp/trash/syslinux-603/bios/linux# ./syslinux -i /dev/sdb1
root@cpfong-1018P:/home/cpfong/tmp/trash/syslinux-603/bios/linux# ls -l /mnt
-r-xr-xr-x 1 root root 122308 Jan 30 10:08 ldlinux.c32
-r-xr-xr-x 1 root root  69632 Jan 30 10:08 ldlinux.sys

# note: sdb NOT sdb1 
# write the Syslinux mbr code (mbr.bin) into the master boot record
root@cpfong-1018P:/home/cpfong/tmp/trash/syslinux-603/bios/mbr# dd conv=notrunc bs=440 count=1 if=mbr.bin of=/dev/sdb

# make sdb1 bootable, you may use fdisk
root@cpfong-1018P:/home/cpfong/tmp/trash/syslinux-603/bios/mbr# parted /dev/sdb set 1 boot on
fdisk
--
Command (m for help): a
Selected partition 1
The bootable flag on partition 1 is enabled now.

# syslinux.cfg
default vesamenu.c32
prompt 0
timeout 600

MENU TITLE Multi Boot Menu Edit by Barry

label 98DOS
MENU LABEL Win98 DOS Simple
kernel memdisk
append initrd=98dos.IMA

# after work
cp xxxx.c32 to sdb1

boot usb can enter dos NOW