grub installation always fails .

[Hamza]

I have a PC with 1Tera hard disk and used to work on windows 10 .. 2 days ago I tried to install Ubuntu using USB ( i tried FAT32 and NTFS Modes .. I don't actually know what they mean but tried both as grub always fails to get installed ) .. I didn't change any settings at this point .. I used my C partition (100 GB) to install Ubuntu on it by dividing it to 10GB swap and 90GB as ext4 root ...
my problem started when a warning appeared asking me if i want to force UEFI Installtion and i choosed "continue in UEFI mode" then the i had this error " 'grub-efi-amd64-signed' package failed to install into /target/. without the GRUB Boot loader,the installed system will not boot. " i cancelled installtion and tried another one but this time i choosed "Go back" rather than continue in UEFI Mode .. and i got another error that grub installtion failed .. i even changed UEFI Mode to Legacy mode and the same issue happened again :) i don't understand what i'm doing but i had to try :D

ProblemType: Bug
DistroRelease: Ubuntu 16.04
Package: ubiquity 2.21.63.4
ProcVersionSignature: Ubuntu 4.10.0-28.32~16.04.2-generic 4.10.17
Uname: Linux 4.10.0-28-generic x86_64
ApportVersion: 2.20.1-0ubuntu2.10
Architecture: amd64
CasperVersion: 1.376.2
Date: Wed Aug 8 17:09:08 2018
InstallCmdLine: BOOT_IMAGE=/casper/vmlinuz.efi file=/cdrom/preseed/ubuntu.seed cdrom-detect/try-usb=true noprompt floppy.allowed_drive_mask=0 ignore_uuid boot=casper only-ubiquity quiet splash ---
LiveMediaBuild: Ubuntu 16.04.3 LTS "Xenial Xerus" - Release amd64 (20170801)
ProcEnviron:
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=en_US.UTF-8
SourcePackage: grub-installer
UpgradeStatus: No upgrade log present (probably fresh install)

[Phillip Susi (psusi)]

Thank you for taking the time to report this bug and helping to make Ubuntu better. This particular bug has already been reported and is a duplicate of bug 1766945, so it is being marked as such. Please look at the other bug report to see if there is any missing information that you can provide, or to see if there is a workaround for the bug. Additionally, any further discussion regarding the bug should occur in the other report. Please continue to report any other bugs you may find.