Install Linux on a partitioned external hard drive

How to install Linux on a partitioned external hard drive?

Yes, it's possible. It's a matter of installing linux, on that parition, and being able to boot to it. I need to explain something though.

When your computer turns on, it immediately goes to your MBR (Master Boot Record). This is a part of your First Hard Drive (If you have other harddrives, you can choose the "first" through your BIOS). There are "Boot Loader" programs that live in the MBR. The regular Windows one is limited, and usually just refers right to your Windows installation on C:\.

When you do a normal Linux installation, it overwrite the MBR with it's own Bootloader program (usually a program called GRUB or LILO). The linux Bootloader Program is usually setup so you can choose which system to install into (or it auto boots the default in X seconds). Good linux installers will autmoatically detect your Windows partitions, and add them very easily.

The thing about external drive is, ofcourse, they are portable. If you installed Linux to the external drive, and the Linux bootloader to your main harddrive MBR, then configuration of the Bootloader is handled by the Linux installation. If something happens to the external drive, you will still be able to load Windows, but you wont be able to config the bootloader without overwriting it with a completely new bootloader.

If the external is very reliable, and always connected, this isn't a big problem. However, one option is to NOT install to the bootloader to your MBR (This is an option you would have to select during the Linux installation). Most Linux installation disks can also be used to boot to a Linux installation on a harddrive. Ubuntu is one (and also a good distro for Linux newbies, http://www.ubuntu.com/ ). You would need the CD to boot to Linux, but the advantage is that the CD is as portable as the external drive.

There are also types of Linux that boot entirely from the CD alone, and you don't need to install at all. (SLAX is my favorite, http://ww.slax.org/ ). This is a good way to try out Linux for a first time aswell.

Sorry if I wrote too much, the stuff about the MBR is very technical, but important to know if you are dual booting with Linux and Windows.

Edit - Just to point out, 30 GiB is more than enough for the average Linux installation. My Linux installation right now is using under 2 GiB (although, it's ultra-streamlined and very customized). I also have a full featured ubuntu, with lots of extra program installed, and it is around 7 GiB. Linux apps are usually A LOT smaller than Windows (aswell is smarter, faster, more efficient, free-er, better, etc.).

It is the media files (movies and music) that will fill up the drive. Linux can easily read Windows (NTFS) partitions, but NOT write to them (easily or safely). If you want to read/write media from both Windows and Linux, you will need to setup a partition with a FAT32 file system. (Which is also read/writable to Mac aswell as Windows and Linux... you probably want your external FAT32 anyways, if it is not already.)