Super User is a question and answer site for computer enthusiasts and power users. Join them; it only takes a minute:

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

I am trying to install ububtu on an external drive.

I am a programmer who wants to start using Linux. I downloaded the usb installer from the ubuntu website and followed all the steps.

But when I get to the part where I have to setup the partitioning, it says an error when moving forward "No root file system is defined".

I've been doing some research and I think that I have to partition the external drive but do not know how to do so.

The problem is that I only want 20gb used from that external drive and let the rest be used for storage.

I am also a musician and use Pro tools so I would like to keep all my files there, but I dont want ubuntu on my main hardrive since the external one is portable.

I'd appreciate it also if you could provide me the steps.

share|improve this question

migrated from Oct 16 '10 at 23:27

This question came from our site for professional and enthusiast programmers.

up vote 2 down vote accepted

This is really quite simple. You don't have to partition it beforehand; Ubuntu's installer can do this.

  1. So when you have the USB (I assume you plugged the USB drive plugged in as well as the hard disk) booted up, you go through the steps like you did before.

  2. Stop when you get to the part that says Prepare Disk Space. Choose Specify Partitions Manually there and then wait for the next screen.

  3. The next screen should look a bit like this:

    enter image description here

  4. From here, you want to try to find your external drive by its capacity (the drive, e.g. /dev/sda or /dev/sdb, not the partition, e.g. /dev/sda1 or /dev/sdb4) which you can get by adding up the size of its partitions (I assume there's only one right now?). It's usually /dev/sdb.

  5. When you figure that out, click on the drive (/dev/sd*) and click New Partition Table.... This'll empty out the drive's partition table on the view so you can start from a clean slate.

  6. Now, with /dev/sdb still selected, click Add... and it should pop up a small window.

  7. On this window, set the size to what you went, set the filesystem to ext4, and set the mount point to / (a forward slash) from the dropdown boxes. / is the root of the whole Linux file structure, so that's important to set.

  8. Click Ok or Apply or whatever and do the same thing again for your storage partition, but this time set the filesystem to NTFS or FAT (your choice) and set the mount point to /home (obviously, /home is where all the user data goes, so that's where you can store everything). Set the size too, of course.

  9. You can then click Forward and proceed on your merry way.

  10. Do the user account thing, but DO NOT choose the option to encrypt your home folder. Else, you won't be able to read the drive from Windows or Mac (side note: if you use a Mac, don't use NTFS back there).

  11. When you get to the really scary Review-this-summary-or-you're-screwed-when-you-hit-Install view,

    enter image description here

click Advanced... and where it asks where the bootloader should go, make sure you put it somewhere on the external drive (same sd* letter as when partitioning) so that it'll work on places other than your computer too.

  1. Click Install and wait.


Oh, and a super important note:

share|improve this answer

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .