Can I dual boot Fedora 16 and Fedora 21

edit

Of course, yes ; Fedora 16 can be viewed as another OS from Fedora 20. But please note that F16 is not maintained anymore, it contains bugs which will not be fixed. The last time I dual boot two linux systems, I used one master (let's say F16) and a slave (let's say F21) seen as an external OS.

Install F20, booting from an installation media (usb key, dvd):

• Use a custom partition scheme to preserve the current F16 partitions
• Remove the separated /boot partition to use the F21 root partition only
• Re-use the /home from F16
• install everything, including grub2 the default F21 bootloader

Setup F16 :

• edit grub.conf , insert the next line choosing the right partition to pass the boot to the F20 bootloader

menuentry 'Fedora20' {
  set root=(hd0,1)
  chainloader +1
}

After booting on F20, you should take care : the default user should have the same uid / guid value than the one in F16. And that's it !