What is the correct/best way of dual booting another Linux distribution (say, Fedora 14) along with Ubuntu 11.04? Is sharing the /home partition with both distros is a good idea? What are the pitfalls I have to be aware of?
Using the same home can cause problems, especially with the configuration files that are in your home directory. All of your personal settings and configurations for numerous applications are contained in your home folder. In addition to the UID (user ID) issue, it is possible that Fedora and Ubuntu use different versions of some applications, which may have conflicting/incompatible config file format(s) and/or locations within your HOME.
But I have a better idea for you: make both Fedora and Ubuntu their own home on a minimum partition and use a shared data partition where you store your own files. When you are done installing both systems remove on both system ~
This not only prevents you overwriting files in your home directory that are different for another OS but when you add a 3rd,4th, 5th OS or when you need to reinstall you can have all the important files back by recreating the symlinks.
edit: here is an example of what can go wrong: Why are my two ubuntu installs on separate partitions sharing the same apt-get data?
This user has 2 Ubuntu's installed: one with classic and one with Unity both using the same /home/.
are being used by both systems since these are in /home/ so updates and software installed affect both installations.
Just install one distro after the other. However, I would strongly recommend against using the same /home location for both as application settings of the two distros would overwrite one another. You can still use the same /home/Documents/ or /home/Pictures etc for both though - this will make sharing files super-easy.
Ubuntu Tweak lets you easily switch the default folder locations:
I use Ubuntu as my base distro and then install any others I use as virtual machines using Virtualbox OSE (available in Synaptic and the Software Centre). It just feels cleaner doing it this way instead of dual-booting. You also have the confidence to add/delete operating systems at will without the fear of messing up your whole box.
Sharing /home folders between systems is a bad idea due to the amount of hidden config files. It's much better to have a centralised file server for your documents. You can set one up cheaply with an external HDD.