How to dual boot Windows 10 and Debian


In this post we will go through the process on how to dual boot Windows 10 and Debian. In this scenario, we have WIndows 10 installed on a single drive, created a separate partition for Debian installation on the same drive and during the setup process, configured the dual boot for both operating systems.

It is advisable to backup your system first before making any new changes, since all this will be performed on a single HDD. Also, check you PC how it boots(UEFI or Legacy - GPT or BIOS partition types) and make sure both OS are installed in the same mode.

Most of the post will be covered with Debian’s default installer, but we’ll also showcase some important steps of process on Debian’s new Calamares installer for Live images which is more beginner friendly. Here you can find a tutorial on how to create a Debian bootable USB in Windows 10

Requirements for this process:

  1. Debian bootable USB
  2. Available free HDD space or a second HDD

Assuming you have Windows first installed, first step is to create a partition for the Debian system. For this you can use a disk management utility in Windows or a third party partition software. There a lot of them that are free and good.

Before you do anything, make sure to backup all the important data you have and do this process only if you have free space on you HDD or if you have a second HDD – that would be even better.

Creating partition for Debian installation

For this tutorial, we will use disk management utility. Start the utility by clicking the right click on the start menu and select the disk management option. When the window gets opened, on the bottom you’ll see all your drives and partitions listed. Next step is to create a new partition that we will use for our Debian installation.

If you have more than one partition on your PC, choose the one which has more free space. In this case, we only have one partition and it’s a Windows partition. So, we will select our Windows partition, click right click on it and select the option Shrink Volume. Once more be sure to have free space on any of your drives.

After you click on the option Shrink volume, it will open you a new window. In this windows you will set up your new partition.

In the field - Enter the amount of space to shrink in MB - you will enter and allocate free space for your new partition. So, enter how much space you want for your new partition to have and click on shrink. Keep in mind again that you need to have enough free space on your drive.

Once that is done, on the bottom of the disk management window, a new partition you created will show up and it will have Unallocated label on it. Next step is to insert your bootable Debian USB on your PC, restart the PC and boot the Debian installation from the USB.

Debian installation(dual boot Debian and Windows 10)

I recommend to choose the installation with the graphical interface.

dual boot windows 10 and debian 10

NOTE - Debian also offers Live images, where you can boot Debian live and test the system and has more simplified installation procedure.

Once you start the installation, first it will prompt you to choose the language, select your location and choose the keyboard layout. After that, it will prompt you to enter the hostname for your PC. By default, this will be already filled but you can change it if you’re going to do networking afterwards.

Next it will ask you for the domain name. You can leave this empty if you plan to use Debian for personal and home use.

Root account setup

In the next screens, you need to set up your root account - Installation will ask first for the password then the next screen will ask you to enter the username for the root account. After that, it will ask you to set up your personal account and the process will be the same.

After the account creation, next step will be to choose your time zone.

Formatting Debian partitions

Now we need to partition our Debian installation. There are two ways to partition the drive, manual and automatic and we’ll cover both of them.

Manual partitioning is for more experienced users with GNU/Linux since it requires more steps to finish the process but it has it’s benefits like creating a separate boot partition which is also covered in this post or installing the Debian on a second HDD.

You’ll get this screen where it will prompt to choose how will you manage the partitions. Select Manual and click continue.

dual boot windows 10 and debian 10

Double click on the partition with FREE SPACE label and click continue.

dual boot windows 10 and debian 10

Choose the option to automatically partition the free space.

If you’re not experienced with Linux, you can go with the first option to place all user directories on one partition, or you want to separate the directories, there are option to make all directories as separate partitions.

If you go with the first option, the installer will format the partition automatically and return to the partition disk menu.

You can continue and finish the partitioning.

Calamares installer partition format

dual boot windows 10 and debian 10

Calamares installer runs partitioning much simpler. In the first picture, if you haven’t created a separate partition for Debian, then just select - “Install alongside” option and on the bottom, move the slider in order to allocate the space for Debian.

NOTE - This can be done if you have plenty of free space on the Windows partition.

Other way is with the option - “Replace a partition”. This option can be used if you have created a separate partition for Debian, then on the slider just select the grey empty bar that represents free space and the installer will do the rest(just like in picture bellow).

Manually partitioning with a separate boot partition

One good reason why this is a good option to create a separate boot partition. If you have Windows 10 installed, by default Windows will create a boot partition which will be used as a default boot partition for your machine. Debian can use that partition as well, it will detect it in the installation. So, if you install Debian on that same partition that will make Windows and Debian to use and share the same boot partition. Nothing wrong with that, but there’s a caveat going with this step.

Eventually over time, Windows with it’s update can overwrite that boot partition and that can cause to loose the boot configuration for Debian, meaning it cause for Debian to be unable to boot at all. Nothing critical and can be fixable by booting the live image and repairing the GRUB bootloader. It does not happen often but It can be a hassle when it happens. But, since Windows 10 recently, has a much more frequent updates and many of them turn out to be unstable, that’s why it’s a smart decision to make a separate Debian boot partition.

For that, again we will go with manual partitioning again. Boot partition needs to be created first before your root partition. Create a new partition, of 1 GB in size(it’s plenty for boot partition), set it as primary and to start the beginning of the drive.

dual boot windows 10 and debian 10

For the partition format or extension, we can go with ext4, partition type select as boot partition, label it boot as well and set the boot flag to on. Just as in the picture bellow.

That was the procedure for the boot partition. The rest of the partition, you can partition as you wish - you can do it manually again or go through the guided process and the installation will partition it for you.

This is how the partition process looks like on the installer from the live image(Calamares installer). Installer from live image also supports ntfs and fat32 extension as well so you can go with that for your boot partition.

dual boot windows 10 and debian 10

In Calamares installer, make sure to set flags - boot and esp for boot partition when you format it as GPT partition type.

Package manager setup

When you click continue, the installation will first prompt you are you sure to make the changes. Click YES and continue again. The installation will install the system and once that is finished, we will need to configure the package manager.

First, it will ask you do you want to use a network mirror - Click YES and continue.

Next step is to choose a Debian server. Installation will automatically choose a server but it’s recommended to choose a server from your country or the closest to your country.

Next to do is to select an archive mirror. Again, you can leave the selection by default but it’s recommended to choose one from your country or close to your country.

On the next screen, it will ask you to set up the HTTP proxy. It’s not mandatory, you can leave it empty. If you need to use a HTTP proxy for an internet connection then you enter the link of your HTTP proxy server.

Choose your Desktop environment you want to be installed. You can install multiple DE’s if you want.

GRUB installation(dual boot configuration)

Now here comes the last step and an important one. The dual boot Windows 10 and Debian setup. The installation will detect another operating system installed on the HDD and it will prompt you to install it’s own bootloader, which is the GRUB bootloader to maintain the OS booting. On the screen you need to select YES and continue.

dual boot windows 10 and debian 10

On the next screen it will ask you on which HDD to install the bootloader. You need to select your main HDD where windows is installed.

dual boot windows 10 and debian 10

If you go with this option, then the GRUB bootloader will be installed on the same boot partition which Windows uses as well and this setup will make for Debian and Windows to share the partition.

If you wish to install the bootloader on the new boot partition that you’ve created separately.The default Debian installer mostly will not prompt where to install the bootloader if it detects a boot partition. The Calamares installer will prompt for bootloader location every time.

Finishing up

And that is it. That was the entire set up, you installed Debian alongside Windows 10 and also set up the dual boot. The installation will finish and reboot automatically. Once the PC boots again, you need to have this bootloader screen first where it prompts which OS to boot, Windows or Debian.


To summarize the article, we showcased the process on how to dual boot Windows 10 and Debian. We reviewed the steps how to install Debian step by step alongside Windows by manually configuring the install wizard and running the manual portioning. Apart from that, we covered the default installation wizard of Debian 10 and the Calamares wizard of Debian 11 and how to configure Calameres to dual boot Windows 10 and Debian 11.

I hope you found the post useful, that the process was easy to follow and that you were able to dual boot Windows 10 and Debian. Thank you for your time…