How To Dual Boot Windows And Debian

Setting up a dual boot with Windows and Debian gives you the best of both worlds — the power and flexibility of Linux, alongside the compatibility of Windows. Whether you’re a developer, a tinkerer, or just curious about Linux, this guide walks you through the process with no fluff, just the steps you need.

What You’ll Need

• A computer with Windows installed
• At least 20 GB of free disk space
• A USB stick (4 GB or more)
• A copy of the Debian ISO (download from https://www.debian.org)
• A tool to create bootable USBs (like Rufus or balenaEtcher)

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Step 1: Back Up Your Data

Before you touch any partitions or operating systems, back everything up. This process is safe if done correctly, but there’s always a chance something could go wrong. Use an external drive or cloud backup.

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Step 2: Free Up Space for Debian

1. Open Disk Management in Windows (hit Win + X, then choose Disk Management).
2. Right-click your main partition (usually C:) and choose Shrink Volume.
3. Shrink at least 20 GB for Debian (more if you can).
4. Leave the space unallocated — Debian will use it later.

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Step 3: Create a Debian Bootable USB

1. Download the Debian ISO from the official site.
2. Use Rufus (Windows) or balenaEtcher (cross-platform) to write the ISO to a USB stick.
3. Make sure the USB is formatted correctly (usually FAT32) and the ISO is written in ISO mode, not DD mode.

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Step 4: Boot from USB and Install Debian

1. Reboot your PC and enter the BIOS/UEFI settings (usually by pressing F2, F12, DEL, or ESC during startup).
2. Change the boot order to boot from USB first.
3. Select your Debian USB and boot into the Debian installer.

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Step 5: Install Debian Alongside Windows

1. In the Debian installer, choose “Graphical Install”.
2. Go through the setup steps (language, timezone, etc.).
3. When you reach Partition Disks, choose:
   • “Manual” partitioning
   • Find the unallocated space you created earlier
   • Create:
     • A root (/) partition (~15+ GB, ext4)
     • A swap partition (equal to your RAM size if you don’t use hibernation, otherwise 1.5x RAM)
     • Optionally, a home (/home) partition for your files
4. Do NOT touch the Windows partition.
5. When asked about the bootloader, make sure GRUB is installed to the EFI partition (usually /dev/sda, not a specific partition like /dev/sda1).

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Step 6: Reboot and Test the Bootloader

1. Remove your USB and reboot.
2. You should now see the GRUB menu — it lets you choose between Debian and Windows.
3. If Windows doesn’t show up, boot into Debian and run: sudo update-grub It will detect Windows and add it to the GRUB menu.

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Common Issues

• No GRUB menu? Check BIOS boot settings or try Boot Repair from a live USB.
• Can’t boot Windows? Make sure you didn’t overwrite the Windows partition.
• Wrong time in Windows after using Debian? Set Windows to use UTC or Debian to use local time.

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Wrap-Up

Dual-booting Windows and Debian can open up new workflows and let you learn Linux without giving up your current setup. It’s a bit of setup work, but once it’s done, switching between systems is as easy as a reboot.

Need help with a specific step? Drop a comment below and I’ll help out.