Multisystem is a free program for several Linux distributions, live or repair systems, that can be installed on the same external disk with the same bootloader. Here, more than 200 systems supported. As an example, a disk USB flash drive, an SDHC card or an entire USB hard drive can be used.

MultiSystem is not only suitable for testing different distributions, but you can also, in some Linux distributions enable the "persistent mode." This allows it to use the stick as a multi-boot system, and the changes performed by the user are saved and available at the next start of the system.

An installation on a USB stick has the advantage that if the use of an optical drive is not possible, usually a USB port is available, which can be booted from. Is it the other way around is not possible to boot with the BIOS from a USB flash drive, so you can create out of the program a CD image, which uses the burned CD boot routine to detect the USB stick and to load one of the systems from it.

MultiSystem uses Grub2 instead of Grub Legacy, and can be run from within Linux Mint to create a Custom Multiboot UFD containing your favorite Bootable Live Linux Distributions.

MultiSystem in brief

• Create your MultiBoot LiveUSB simply with MultiSystem.
• You just have to Drag/Drop your.iso on a window and that's it!
• MultiSystem enables a LiveUSB to do everything, ideal for exploring different Linux distributions do not install them on your PC, and it seamlessly.

Multisystem Prerequisites:

• Ubuntu Linux or Ubuntu Based System (can use an Ubuntu CD or USB)
  
• A USB Flash Drive (to use for your MultiBoot USB)
  
• Working Internet Connection
• install-depot-multiboot.sh.tar.bz2

How to Install the Multisystem LiveUSB Tool

1. Download and Open the Script with the Archive Manager
2. Extract the install-depot-multiboot.sh Script to your Desktop
3. Double Click install-depot-multiboot.sh from your desktop and select the option to "Run in Terminal"

How to Use the Multisystem LiveUSB Tool

1. Insert a USB Drive
2. Launch the Script via Applications > Accessories > MultiBoot
3. Select your USB Device from the list and click Validate
4. Now simply Drag and Drop an ISO into the Window to add the Distribution (repeat the process to add more ISOs)
5. Once finished, restart your PC, set your boot menu to boot from the USB device, Select the Distro you want to Boot and enjoy!

References used:

1. http://wiki.ubuntuusers.de/MultiSystem
2. http://www.pendrivelinux.com/multiboot-create-a-multiboot-usb-from-linux/