This howto will show us how to manually create a bootable USB (flash) drive using the EXTLINUX bootloader.
Unlike SYSLINUX who installs on FAT formatted drives, EXTLINUX can be used for EXT2/3/4 and even btrfs formatted drives.
EXTLINUX is easier to use than GRUB.
Why use the EXT2 filesystem? It is recommended for flash drives as it is a non-journaled filesystem so the write operations are reduced compared to other journaled filesystems.
See http://en.wikipedia.org/wiki/Ext2 for more info.
Have you ever tried to install a modern Linux distro onto a small capacity (usually 32 megs or even less) usb drive or compact flash card?
Even with a minimal install, such a distribution will not fit! Major Linux distros like Debian/Slackware/Arch/etc need a bare minimum of 300-400 megs of disk space.
The only minimal system I have been able to install so far on a 128Meg disk is NetBSD ( http://www.netbsd.org ).
But there is a way to achieve such a thing : we will be using Buildroot in order to generate a very small (embedded) Linux system (targeted at a standard intel x86 computer)