I have a PC with a 1 TB HDD partitioned for NTFS, a single C: drive, and Windows 10 as the operating system.

I want to dual boot my computer with Ubuntu running alongside Windows. How will Ubuntu partition my drive for the dual boot?

Note: I will be using more of Ubuntu than Windows. I will use Windows only for MS Office and a few other tasks.

  • the ubuntu installer will partition perfectly your HDD, you just have to precise the space for it (use the case "Another case" in the select formatting menu, add a new partition in ext4 of your space, select it and continue the installation)
    – damadam
    Jul 12 '18 at 7:25
  • when you are installing Ubuntu there will be an option Install Ubuntu alongside windows. Just go with it select how much space you want. that's it. Jul 12 '18 at 7:30
  • 2
    Both options are possible, but the option provided by Jahirul Sourav will be easiest as it provides automatic partitioning. Make sure before starting the installation of Ubuntu that you Windows system is set to fully shutdown. This means: disable the "Faststart" option, which in Windows is enabled by default. With faststart enabled (the default), Windows does not fully close the partition when shutting down. If the partition is not fully closed, the Ubuntu installation program will not be able to resize it.
    – vanadium
    Jul 12 '18 at 7:46
  • UEFI or BIOS. If Windows pre-installed it will be UEFI. If an upgrade from Windows 7, probably BIOS with MBR and its 4 primary partition limit. Only use Windows to shrink NTFS partition and reboot immediately to let it run chkdsk which is required after any resize. Then use Ubuntu installer to create / (root) or partition in advance with gparted.
    – oldfred
    Jul 12 '18 at 16:58

If you select the Install Alongside Windows option during the Ubiquity install process, Ubuntu will use gparted to downsize the NTFS partition and create an Ext4 partition for /root automatically, whether you have a GPT partition table (normally found with Windows 10 UEFI installs), or an MBR partition table (normally found with upgrades from Windows 7 legacy installs). Ubiquity will not disturb any other partitions such as the EFI Boot or Recovery partitions created by Windows 10 during its install process.

However, Windows does not share well with others (and more on that shortly). You must disable the "Faststart" option within Windows (and, preferably, also delete %SYSTEMROOT%\hiberfil.sys by running powercfg.exe -h off from an elevated command prompt) before rebooting. Then, if you have Secure Boot in your BIOS, you have to go into the BIOS Setup to turn that off as well, before you start the Ubuntu install. Windows does not fully close the NTFS partition in its shutdown if faststart is on, and that's the Windows 10 default(!). If the partition is not fully closed, Ubiquity can't resize it.

Ever since 17.10, Ubiquity has not created a swap partition by default, instead using a swap file, as swap file speed issues have been resolved.

If you select Something else during the Ubiquity installer run, you can custom-assign the space allotted to NTFS and Linux, specify a Linux filesystem other than Ext4, or make other customizations. Since you can reallocate space later using a LiveUSB flashdrive with gparted, the Alongside Windows option is more popular, and is best left for folks who can't remember where their Linux training wheels are.

Please do consider that Linux reads (and writes) files in NTFS partitions, but Windows does not read files in Ext4, and the open source driver for Windows to access Extn partitions, ext2fsd, has left a trail of broken filesystems behind it. Microsoft does not like you using Linux apps to access files in NTFS, so you may wish to add a FAT32 partition if you have to work on files from both Windows and Linux.

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