Dual Boot with Windows
Last updated
Last updated
Ubuntu full disk encryption (FDE) is not possible with dual-boot
Legacy/MBR allows only 4 primary partitions
GPT (GUID Partition Table) allows 128 primary partitions
Ubuntu install partitions (for / and swap area) can be either primary or logical
Never defragment an SSD
Don't install Ubuntu using a computer that already has Ubuntu, especially if it has a dual-boot. It seems to corrupt the bootloader of the existing install
Get a USB drive at least 8GB
Install the desired Ubuntu image using either or
The drive must be NTFS. FAT32 drives can't be shrunk.
Backup the entire drive (Windows) if desired
Shrink the existing drive to make room for the Ubuntu partition
Check free space on the drive. You must have at least enough free space as the desired Ubuntu partition size. If not, delete some files.
Always do this from within Windows
Use Windows Disk Management
Control Panel -> "Create and format hard disk partitions"
Start -> Run -> "diskmgmt.msc"
Right click on the Windows partition -> "Shrink volume"
Make the new volume large enough to hold both the Ubuntu install and a swap area
Recommend swap partition 1-2x installed RAM
Creating a dedicated swap partition might not be necessary anymore because Ubuntu creates a swap file automatically, but it doesn't hurt to do this. Ubuntu still recognizes it and uses it.
If the "Shrink volume" tool provides insufficient space available to shrink, follow these guides:
DO NOT DEFRAGMENT AN SSD. Only defrag a HDD.
You probably don't need to defrag. It takes a long time, so try everything else first. Disk Cleanup had the most impact for me.
Empty recycle bin
When this is done, you should have a new "free space" / "unallocated" partition large enough to hold the Ubuntu partition and a swap partition.
This method is preferred. It is also required if the Windows system is already set up for UEFI boot.
Follow this guide:
This guide is for Legacy/MBR installs, but 99% of it is the same, and it's a great simple guide
Make all new partitions logical. They can be primary, but logical works fine and it avoids potential issues with having too many primary partitions.
For UEFI installs, don't create the /boot partition. Instead, make sure there is an existing "efi" partition from Windows, and if the Ubuntu installer gives you a dropdown to select the location of the boot loader, select the partition with "Windows Boot Manager" (the "efi" partition).
There is a partition/directory on each physical bootable disk that contains one or more boot loaders. When you install Ubuntu, the Ubuntu bootloader (Grub) gets added to this partition at \EFI\ubuntu\
The Ubuntu bootloaders are:
\EFI\ubuntu\shimx64.efi - Windows signed (preferred)
\EFI\ubuntu\grubx64.efi - Not signed by Windows
If there is NOT an existing "efi" partition, create one.
Mount point = /boot/efi
Size = 200MiB
Format = FAT32
Flag = "boot"
If there is already an "efi" partition, do NOT make another one.
This is what the "Something else" (manual installation) screen should look like in the Ubuntu installer when everything is configured properly.
After clicking "Install Now," review the changes and confirm that only the intended partitions will be formatted.
Other References
Follow this guide:
Make all new partitions logical. They can be primary, but logical works fine and it avoids potential issues with having too many primary partitions.
If you can't boot into Ubuntu after installing on a separate partition, try the following:
Windows: Disable hibernate
BIOS: Disable fast/quick boot
Turn OFF Fast Startup
Windows 10 -> System Settings -> Power & Sleep -> Additional power settings -> Choose what the power buttons do -> turn OFF "Turn on fast startup (recommended)"
Set the boot manager to Ubuntu (grub) in Windows
If the above works, you will see this success message:
Run bcdedit /enum and confirm that Windows Boot Manager is now using shimx64.efi or grubx64.efi.
Reinstall Ubuntu: Make the install partition Logical
Reinstall Ubuntu: Make the install partition Primary
If you get this error, your bootloader file is not located where it should be on the disk, or it has a different name than what the system is expecting.
This happened when I tried booting off my live install USB drive, so somehow the drive got messed up. I fixed this buy just re-flashing the Ubuntu install disk. I could have also fixed it by manually changing the bootloader files on the disk.
Change what boots by default when you turn on the computer.
Very detailed guide:
Method 1 =
Method 2 =
