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When installing Ubuntu I unknowingly set my EFI mount to the windows EFI partition. Now I need to delete windows along with its EFI partition for a fresh install. I already have another partition prepped up to be the Ubuntu EFI boot partition. How do I migrate /boot/efi to that partition?

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Why change. You can only have one efi partition per hard drive and Ubuntu easily uses the one that already exists. With gparted it is the boot flag on a FAT32 formatted partition that defines the efi partition. But only one per hard drive. –  oldfred May 10 at 16:32
    
It's perfectly legal to have multiple EFI System Partitions (ESPs) on a single hard disk, although the Windows installer gets confused by such a setup. That said, I agree that there's no need to change. –  Rod Smith May 10 at 19:47

3 Answers 3

An EFI System Partition (ESP) is simply a FAT32 partition with a GUID type code of C12A7328-F81F-11D2-BA4B-00A0C93EC93B (or 0xEF on an MBR disk). Most partitioning tools have some other way of displaying the GUID type code, because GUIDs are so cumbersome. In parted, GParted, and most other libparted-based tools, it's shown as a "boot flag" being set on the partition. (Note, however, that in libparted-land, the "boot flag" on a GPT disk is unrelated to the "boot flag" on an MBR disk. AFAIK, libparted provides no way to correctly label an MBR ESP.) In GPT fdisk (gdisk, sgdisk, and cgdisk), an ESP has a type code of EF00. Non-Linux tools have their own ways to identify ESPs.

Thus, to create a new ESP, you would:

  1. Boot to any Linux tool that lets you partition the disk. This could be your existing Linux installation or an emergency disk/live CD -- but if you use your regular installation, be aware that you may be limited in what you can do, because many partitioning tools limit what you can do to a disk with partitions that are mounted.
  2. Launch the partitioning tool of your choice.
  3. If necessary, create a new partition. I recommend making it at least 550MiB in size. Note that you may need to shrink existing partition(s) to make room.
  4. Place a FAT32 filesystem on the partition. Some tools, such as GParted, make it possible to combine this step with the previous one.
  5. Mark said partition as an ESP.
  6. Unmark or delete the old ESP.
  7. If necessary, save your changes.

For making partition table changes, there's no need to be concerned with your boot mode -- you can use EFI mode or BIOS mode as you see fit. (That said, some computers make it easier to boot from USB or CD-R in one mode or another.)

I agree with oldfred that creating a new ESP is unlikely to be necessary in your scenario. If you want to completely erase the Windows boot loader from the ESP, feel free to do so -- it would be the /boot/efi/EFI/Microsoft directory tree once Ubuntu is installed. Note that this will not remove the Windows boot loader from the firmware's boot manager menu. To do that, you'll need to use efibootmgr, as in:

$ sudo efibootmgr 
Timeout: 10 seconds
BootOrder: 0000,0004,0001,0002
Boot0000* rEFInd boot manager
Boot0001* PATA: HP DVD Writer 1040r     
Boot0002* SATA: ST32000542AS             2
Boot0003* SATA: TOSHIBA DT01ACA300       3
Boot0004* Windows boot manager
Boot0008* INTERNAL EFI SHELL: ST32000542AS
$ sudo efibootmgr -B -b 4

This example deletes boot option #4, which is identified as "Windows boot manager." (I don't recall the name that Windows uses by default; I edited this example from one of my systems on which Windows is not installed.)

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Thanks It worked! –  Mythreya May 12 at 11:14

Try using the Ubuntu's disk manager before installing it. Allow bios to be in CSM boot mode before installing "try ubuntu", disks, click on the partition needed format, leave blank or you can format to ext2. Restart, bios back to UEFI boot mode, install should work fine.

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Using a bootable USB flash drive with your version of Linux installed including Gparted.

Boot from the flash drive by accessing boot order in your BIOS.

On my Asus laptop, the Aptio BIOS, it was necessary to disable FastBoot and SecureBoot before the BIOS would enable Flash drive booting as an option.

Once you can boot from USB, run your Distro with the "Try Ubuntu" option. Now that you are running from the Flash Drive, using Gparted to manage your partitions is fairly straightforward.

Using Gparted while logged in on your HDD Distro is risky.

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