Multi-booting (automatic way) several Ubuntu based distributions

There is a simple way to boot from different ubuntu .iso images saved on the same media, but a manual intervention is needed in order to rename some files before (re)booting.
It is possible to automate it: it's tricky, but it works.

Briefly:

1. make an usb stick (or hard disk) FreeDOS bootable;
2. put the .iso images on it;
3. put the correct pair of kernel and initrd which boots the .isos;
4. edit (fd)config.sys and autoexec.bat in order to make a menu and a batch that renames some files and boots (using Grub4DOS).

In detail (with the goal of booting the "alternate" distro of kubuntu hardy in either i386 or amd64 flavour):

1. make your usb device boot any (in principle) OS capable of file manipulation. The plain old DOS is enaugh (and fast to load) but not free. FreeDOS is a good choice and making an usb stick FreeDOS bootable is simple;
2. make a folder called "hardy" under the root;
3. download the alternate iso images and put them into the folder "hardy";
4. rename them "i386-k.iso" and "amd64-k.iso" for short;
5. under the folder "hardy" make two sub-folders "i386" and "amd64";
6. download the proper (check here for details) pair of kernel and initrd of each distro and put them into the corresponding folder;
7. get Grub4DOS and put the dos executable "grub.exe" in the root folder (it will be used to boot the kernel which in turn will run the installer on the .iso image);
8. make two configuration files for Grub4DOS to load the proper kernels;
   the first "i386-k.lst" (add kernel options as needed):
   

   default 0
   timeout 1
   title i386
   root (fd0)
   kernel /hardy/i386/vmlinuz root=/dev/ram0 noapic
   initrd /hardy/i386//initrd.gz
   boot
   

   
   the second "amd64-k.lst" (add kernel options as needed):
   

   default 0
   timeout 1
   title amd64
   root (fd0)
   kernel /hardy/amd64/vmlinuz root=/dev/ram0 noapic
   initrd /hardy/amd64/initrd.gz
   boot
   

9. in the root folder, make an "fdconfig.sys" file, which acts as menu:
   

   switches=/F /N
   menudefault=0,30
   menu Kubuntu USB installer
   menu
   menu 0 - Exit to FreeDOS
   menu 1 - Install from kubuntu-8.04.1-alternate-amd64.iso
   menu 2 - Install from kubuntu-8.04.1-alternate-i386.iso
   0?rem
   1?rem
   2?rem
   

10. in the root folder, make an "autoexec.bat" file, which manipulates files and invokes the loader:

    rem common preparation
    cd \hardy
    ren *.iso *.isn
    
    rem select distro
    if "%config%"=="1" ren amd64-k.isn amd64-k.iso
    if "%config%"=="2" ren i386-k.isn i386-k.iso
    
    rem run distro
    if "%config%"=="1" \grub --config-file=\hardy\amd64-k.lst
    if "%config%"=="2" \grub --config-file=\hardy\i386-k.lst
    
    cd \

unmount the usb device to be sure all get saved and reboot.

Multi-booting (manual way) several Ubuntu based distributions

As for Gentoo distributions, for some reasons I need to carry with me different Ubuntu distributions (x86, amd64, live, alternate, etc.) on the same usb disk and to be able to boot and install from them. You (quite) cannot boot directly from the .iso image (with some other distros you can, i.e. quantian). You (quite) cannot put them in a single partition because they all share the same directory structure and jailing each one in a sub-directory did not work. The easiest way is to have each distro in its own partition and a multi-boot scheme for the usb disk.
As stated in the page linked above, it is possible to use a pair of kernel and initrd to load the installer from an .iso image.
If you have several .iso images (related to the same version of the distro) in the same partition, you can choose which one to load from, by renaming the other ones with an extension different from ".iso". The boot process automatically loads and installs from the first image it finds.

Boot and multi-boot related stuff

Useful references:

• boot managers:
  
  
  
  • GRUB
  
  
  • GRUB2
  
  
  • GRUB4dos : tips and a good guide
  
  
  • superGRUB
  
  
  • SMB
  
  
  • PLoP
  
  
  • LILO
  
  
  • ISOlinux, SYSlinux, EXTlinux
  
  


• boot from images:
  
  
  
  • direct from ISO, through some parameter in kernel options line, like knoppix and quantian
  
  
  • install distros from HD
  
  


• booting tips:
  
  
  
  • Just booting tips
  
  
  • Boot from one kernel to another kernel without rebooting the system
  
  
  • for GRUB4dos
  
  


• bootable iso images