I can't answer your questions concerning XiaoKJ chainloading with several instances of the bootloader installed. It sounds too difficult for me for what you do and (probably) isn't necessary.
I also advice you to read the chapter
Preparing the disks in the Gentoo handbook, it explains to you the basics of partitioning.
The partitions that can be shared between distros are these:
swap can be painlessly overwritten by any distro since it's just swapping space for data that doesn't fit into your computer's RAM anymore. As a matter of fact, if you have lots of RAM in your machine so it never needs to swap memory, you can even install your distro without a swap partition. (I still have one, just to be on the save side)
/home can be overwritten by any distro, too, and will even increase your comfort. Let's say you install SuSE and Firefox. After that you tweak Firefox according to your desire and Firefox saves your settings in your /home folder (in my case /home/parcival/.mozilla/firefox ). Let's say next you install Gentoo and Firefox with it. Guess what happens: upon first start Firefox checks if there's already a profile saved in your /home folder and automatically integrates the settings you already did earlier rather than creating a new profile. :) The same's true for pretty much every Linux application there is. The only problem you can run into is if you are using very different versions of the same program in various distros.
/tmp can be easily overwritten, too, since it holds only temporary files. Once you reboot your computer, it doesn't matter what happens to them. Generally speaking, the same is true for
/var (for example in case you are running a file server, you wanna be careful with /var since many mailserver programs store the accounts in a subdirectory of that folder).
To give you an idea how it can be done, I'll tell you the story of my SuSE/Gentoo dual boot I once had. I wanted a computer with an easy distro that would alsways work (SuSE) and a "bleeding edge" distro to tinker and mess with (Gentoo) even for the risk it may not boot properly - that's why I had SuSE as my "rescue distro" installed. ;) My computer had two ordinary 40GB IDE harddisks.
First I booted the SuSE installation CD. In YaST I made these settings when I came to the partitioning part:
- On the master disk (/dev/hda) I created a 10GB / primary partition for SuSE.
- After that, I created a 1GB primary partition for swap.
- After that, I created a 23 GB primary / partition for Gentoo.
- Now the fourth partition had to become an extended partition since I had still more than one to go, so I made one in YaST and filled it with 5 GB /var , 800MB /tmp and 200MB /boot.
- After that I filled my entire slave harddisk with a 40 GB primary /home partition - it's always a good idea to have one's private files on a less endangered disk. ;)
- Before finishing the SuSE partitioner I had to indicate SuSE should mount the freshly created partitions for the rest of the installation so it doesn't put everything into my first / partition. (if the partitions are not being mounted correctly, everything will be installed into subfolders of your / partition. if they are being mounted correctly, all files belonging to the /boot folder will be written to the partition you designed for it, etc.) Finally I also said that I wanted GRUB to be installed in the MBR of my master disk. (no need to tell where the GRUB config files go since we already said previously which partition needs to be mounted as /boot :) )
- The rest of the SuSE installation was just sit and watch.
- Then I proceeded with the Gentoo installation. When I came to the point where the partitions need to be mounted for the installation, I mounted the partitions that can be shared according to my own partitioning shame instead of using the default Gentoo scheme.
- The rest of the installation went as any Gentoo installation does except for the bootloader which I did not install.
- Finally I rebootet my computer and it went straight into SuSE, which is no surprise since the config files written by SuSE into /boot have no clue that there's also a Gentoo sitting on the disk. All that is left to be done is firing up YaST again (or open /boot/grub/menu.lst in a texteditor) and create a new entry pointing to the Gentoo kernel image. VoilĂ*, it's all done.
The same startegy basically applies for any multiboot computer, just modify the number of partitions accordingly. Install the most automated distro first and the one allowing the most manual tweaking the last. The most difficult part is to choose wisely your partitions' sizes, especially if you need an extended partition. Furthermore, if you want Microsoft Windows on your computer,
Windows needs to be installed
first on the
first primary partition of your master disk or you will have a very unhappy day. After that you can proceed with the Linux installation(s) as usual.
HTH.