How to Uninstall Ubuntu From Your Computer

Make room for a new OS

Like with ordinary software, users occasionally migrate between operating systems as their needs dictate. Unlike with ordinary software, though, removing an OS is not as simple as uninstalling it from a menu, but requires wiping part or all of the hard drive to make room for a new OS.

If, as in this case, your computer runs only Ubuntu and you want to make room for something else, you have to erase your hard drive. Before proceeding, it should be noted that these instructions are not applicable if you have a dual-boot setup with Ubuntu and something else, as they will end up erasing all your installed OSes.

There are two main methods for doing this, the quick way and the secure way. The quick way is to just delete the partition headers that tell your computer how to read the data, making it as good as deleted as far as your computer can tell. This, however, leaves all your data just as it is, meaning that your data is forensically recoverable by certain programs. The secure way, on the other hand, is to overwrite the hard drive with a hard drive-sized string of random numbers. Although this takes several hours, and can’t really be interrupted (i.e. you should do it in one go), it writes over your data with indecipherable nonsense.

Both methods involve live-booting, as you can’t fully and properly delete an OS while that OS is running.

Computer repair concept, wrench on motherboard close up
alfexe / Getty Images

Determine Your Drive’s Size

Before booting into your live system, you will have to figure out the size of your computer’s onboard hard drive. This is to ensure that you overwrite the correct hard drive, as the system also recognizes the USB flash drive you live-boot from as a hard drive.

Start by removing any other USB devices from your computer. From here, boot into your current Ubuntu installation, open up the “Terminal” application, and run the following command.

sudo fdisk -l | grep Disk
Ubuntu desktop with a terminal open running commands

This command runs a program which lists all detected (i.e. plugged-in) hard drives and then filters the output down to just the first line of information for each drive. Enter your user password, and after the terminal returns the filtered list, look for a line that starts (after “Disk”) with “/dev” but does not contain the word “loop”. After the first colon of this line, you should see the size listed. Write that number down, power off your machine and proceed to the actual overwriting.

Live-Boot With Ubuntu On A USB Drive

Since you are trying to remove Ubuntu, you probably still have the USB drive that you installed it from. Use this for live-booting over your Ubuntu installation to be deleted, so that your computer’s onboard hard drive will not be accessed at all while performing the wipe. If you don’t have your Ubuntu USB anymore, you can make one yourself.

Fast Deletion With the GParted Application

If you find running terminal commands intimidating and just want to quickly trash your hard drive's data with a few taps, you can use a graphical disk management utility that comes preinstalled on Ubuntu called GParted.

Once you are booted into your live session of Ubuntu, find GParted in your application menu and open it. From here, do the following to delete your hard drive data.

Ubuntu with the GParted application open and a disk partition selected
  1. Select the line with the Size matching the hard drive size you recorded from the steps in the last section.
  2. Hit the icon with the red slash-through circle in the upper-left of the window.
  3. Select the green check mark icon to the right of the now-grayed out delete icon (above).

This will permanently delete your operating system and all the data stored on it, so be very sure before confirming.

Once you are done with this, simply close GParted and shut down the live system and your onboard hard drive will be blank and ready for a new OS.

Fast Deletion With A Header Overwrite

After booting into a live Ubuntu session, open up the “Terminal” application and run this command to identify all disk devices.

Ubuntu Terminal application after running the "lsblk" command

There should only two results that don’t contain “loop”: one representing the USB the live session is running from, and the other representing your hard drive. Make note of the name under the “NAME” column which corresponds to the size your wrote down from the above verification process.

Now, run the following in your terminal where "hd_name" is the name you noted from the previous step

sudo wipefs --all /dev/hd_name
Ubuntu Terminal application with a command ready to be executed

Your partition table headers are now gone, which means that your computer will, for all intents and purposes, think your hard drive is empty.

Thorough Deletion With A Full Disk Overwrite

The steps for this are initially the same as those for wiping the disk headers: start by live-booting your USB, opening up a terminal and determining the hard drive’s device name using the “lsblk” command. Again, the name (under “NAME”) in the row with a size matching your hard drive’s is the name of the drive to be wiped.

From here, run the following command, with “hd_name” replaced with the name you noted when you ran the "lsblk" command.

sudo dd if=/dev/urandom of=/dev/hd_name bs=4096 conv=notrunc iflag=nocache oflag=direct
Ubuntu Terminal application with command ready to be executed

The “dd” command reads and writes raw bytes. While there is a lot going on in this command, the gist of all the options is that “dd” is reading data from your system’s random number generator and writing it in 4096-bit chunks directly to the hard drive, with no shortcuts taken for generating those random numbers.

Now you wait. A lot. When it’s done, though, you will have a drive filled with random, useless data, such that your previous data will not be easily recovered. 

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