I think at some point of time, every Linux user try to setup multiboot system just out of curiosity or to test new distros.

I have installed 6+ OSes in my test machine and it's really easy to setup multiboot system. My test machine has 80GB disk too.


* I would suggest you to create all partitions before starting installation of any distro.

* You are planning multiboot, it means it is not a production machine and there is no need to assign lot of space or create complex partition system. 8-12GB space is enough for any main-stream distro.

* 1GB SWAP is more than enough and all distros can share
same partition.

Recommended Partition Structure

/dev/sda1 SWAP - 1 GB
/dev/sda2 25 GB for Data sharing ( docs etc. )
/dev/sda3 - Extended Partition
/dev/sda5, 6, 7, 8, 9...... - Logical partitions inside Extended partition, 9GB each. You can create 60+ Logical Partitions inside an Extended Partition.

Create all partitions before starting installation of first distro.

* Start installation of first distro and select Manual Partitioning in Partition section. Assign / mount point to /dev/sda5. Installer will detect SWAP itself and use it.
* Start installation of second distro and select /dev/sda6 as /. Installer will detect SWAP and other installed distro. Installer will setup dual boot and use SWAP as its own partition.

Keep on installing other distros unless whole space get exhausted or you find a distro of your liking and stops distro hoping or you decides something else to do with available space !