how-to-create-a-bootable-usb-from-an-iso

Install the .iso contents non-destructively onto a USB partition. Leave out all the partitioning or formating stuff to prepare an existing and used USB drive for DSL booting:
Note: All path names are examples! Please adapt or you may corrupt existing partitions or files.

1. Mount USB drive, with e.g. mount /dev/sdx1 /flash – can be either FAT16 or FAT32!
2. Mount ISO image, with e.g. mount /tmp/dsl-3.2.iso /tmp/iso -o loop
3. Copy all contents from ISO to USB drive: cp -vr /tmp/iso/* /flash/
4. Rename and move syslinux files to root directory: mv /flash/boot/isolinux/* /flash/
5. Rename isolinux.cfg: mv /flash/isolinux.cfg /flash/syslinux.cfg
6. Unmount USB drive: umount /flash
7. Install syslinux: syslinux /dev/sdx1 and eventually set the MBR boot flag for this partition (with fdisk).