1. Abinav_Shankar's Avatar
    Hi,

    I have Windows 10 and Ubuntu 20.10 installed on two separate hard disks. There are problems with my Windows 10 and refreshing or resetting solves the problem only temporarily (the issues come back after two or three logins). I am planning to clean install Windows 10 from USB. I have all my personal files in ubuntu. Will clean installing W10 affect my Ubuntu files? Is it safe to proceed without any additional setups?

    Thanks.
    03-27-2021 02:32 AM
  2. Ecm's Avatar
    If Ubuntu and all your files are on a completely separate drive (not a portion), then you can be 100% certain by pulling that drive before wiping and reinstalling Windows.

    I’d suggest cleaning the Windows drive using diskpart before installing. It’s always nice to be certain there no junk left over.
    excalibur1814 likes this.
    03-27-2021 12:21 PM
  3. me just saying's Avatar
    no matter what you do, ubuntu will be affected. even if you pull the drive, you could lose grub. It may have to be recreated. IMO, it is always good to create a backup of all important files when you do anything major like you are planning - accidents happen.
    03-27-2021 01:25 PM
  4. YamiYukiSenpai's Avatar
    I believe I did this before, but it has been a while since I reinstalled Windows.

    I have an old laptop that's quad-booting (Ubuntu & Windows are in one drive). If you have Windows 10 on the same disk, you can select the largest Windows partition (the NTFS one) at install time (I think even if you delete every partition Windows uses, recreating it from the freed space shouldn't touch the other partitions).

    Assuming GRUB disappears, you can 1) select the Ubuntu partition at boot time, or 2) create an Ubuntu live USB, and reinstall GRUB.

    When you reinstall GRUB, you have to make sure that you mount the Ubuntu partition & the EFI partition. I'm going by memory so I suggest you or someone here look it up to make sure that I was correct or didn't make a typo:
    1. List the disks that are in your system.

      sudo fdisk -l

      It'll have an output similar to this

      Disk /dev/sda: 238.49 GiB, 256060514304 bytes, 500118192 sectors
      Disk model: Samsung SSD 850
      Units: sectors of 1 * 512 = 512 bytes
      Sector size (logical/physical): 512 bytes / 512 bytes
      I/O size (minimum/optimal): 512 bytes / 512 bytes
      Disklabel type: gpt
      Disk identifier: BD7EBAEA-CA89-424C-99FC-914DB87E6AC9

      Device Start End Sectors Size Type
      /dev/sda1 2048 976895 974848 476M EFI System
      /dev/sda2 976896 499337215 498360320 237.7G Linux filesystem

      If you have an NVME drive, instead of something like "sda1", it'll look like something like "nvme0n1p1"

      We'll use my output as an example. I bolded the ones you should pay attention to.
    2. Mount the Ubuntu partition & install GRUB

      su
      mount /dev/sda2 /mnt
      mount /dev/sda1 /mnt/boot/efi
      mount --bind /dev /mnt/dev
      mount --bind /dev/pts /mnt/dev/pts
      mount --bind /proc /mnt/proc
      mount --bind /sys /mnt/sys
      chroot /mnt
      grub-install /dev/sda
      update-grub
      Unmount the partition and restart

      exit
      umount /mnt/sys
      umount /mnt/proc
      umount /mnt/dev/pts
      umount /mnt/dev
      umount /mnt/boot/efi
      umount /mnt
      restart


    Found a post in Ask Ubuntu that might help under the title "How can I reinstall GRUB to the EFI partition?". This forum wouldn't let me paste that link.
    Last edited by YamiYukiSenpai; 04-04-2021 at 10:42 AM.
    04-04-2021 10:21 AM

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