I plan to partition my hard drive so I can install fluxubuntu, minimal ubuntu with IceWM, ubuntu, and windows. (This thread is not about windows, that is just incidental) I have heard that I should use a partition for each OS, and a seperate partition for data, and that it is more secure that way. (as long as you apply appropriate security measures) I have also read that one should make partitions for system files(files that one does not want people to have writable access, such as the etc directory) My question is, what size should I make the OS partitions for minimal ubuntu with IceWM, FLUXUBUNTU and ubuntu, and are there system files that could be easily shared between them. finally, it seems obvious that all three OS's can share the same data partition, and swap partition, but if someone can confirm that I would appreciate it.

Thanks
Paul

Consider

/ for Ubuntu 18+ GB
/home for Ubuntu 9+ GB

/ for fluxbuntu 9 GB (you can make it smaller)

/data partition 90+ GB (use xfs)

/ for minimal buntu 5 GB


/swap 2GB (common)

Some things you might want to consider:

If you have any logical partitions then you are limited to three primary partitions (you can have four primary if you have zero logical).

I've read that Windows will only install into a primary partition. Linux doesn't care.

Partitions physically near the beginning of the disk will have higher performance (fewer/shorter seeks and faster transfer rate). It is tricky but possible to put logical partitions physically before primary partitions.

Each Linux install should have its own partition for / but I don't see anything in your question or the answers you got so far regarding the three choices for /home
1) Share /home between Linux installs
2) Have /home as just a directory in the / partition of each.
3) Have a partition for /home for each Linux install.

I don't know whether (1) is practical at all. I think (2) is the cleanest approach for supporting several Linux installs.