I have Windows 10, so I have EFI partition, but during Ubuntu installation I forgot to select EFI partition. Now I always should to turn on UEFI mode if I wanna to use Windows. Can I enable EFI partition for Ubuntu after installation ?
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2Possible duplicate of Attempted Installing Ubuntu on Windows 8.1 UEFI, Confused about booting in UEFI, Legacy Mode – Rod Smith Mar 29 '16 at 13:11
1 Answers
Can I hint you towards this article https://help.ubuntu.com/community/UEFI
Creating an EFI System Partition If you are manually partitioning your disk in the Ubuntu installer, you need to make sure you have an EFI System Partition (ESP) set up. This partition holds EFI-mode boot loaders and related files. If your disk already contains an ESP (eg if your computer had Windows 8 preinstalled), it can be used for Ubuntu too. Do not format it. It is strongly recommended to have only 1 ESP per disk.
An ESP can be created via a recent version of GParted (the Gparted version included in the 12.04 disk is OK), and must have the following attributes:
Mount point: /boot/efi (remark: no need to set this mount point when using the manual partitioning, the Ubuntu installer will detect it automatically)
Size: minimum 100Mib. 200MiB recommended.
Type: FAT32
Other: needs a "boot" flag.
I have never done this myself but remembered reading about it. Maybe you could also try the magic of boot repair? https://help.ubuntu.com/community/Boot-Repair Sometimes it's also just easier to reinstall Ubuntu...

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100 or 200 is not enough. Especially for dual boot. It gets especially complex if your efi partition is first and windows is next and ubuntu is after that! So do yourself a favor and go for 500 mb. Even if you have a 32gb sdd as your hard drive like me. I actually recently installed a fresh windows 10 that already has november in it. I booted and installed in legacy. Same with lubuntu. For dual boot, do yourself a favor and stick with legacy. My latest bios upgrade seems to forget the trusted non windows efi files. – Bhikkhu Subhuti Mar 29 '16 at 11:29
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