Installing ubuntu alongside Win 10 - grub_amd64_signed error

Question

Currently have windows 10 installed on my laptop (LENOVO G50-70, i5-4th gen, 6gb Ram and 1TB hdd).

I found out by trial and error that I can't have more than four "primary partitions" and so I played around with disk management in windows and got around 100gb of free space (Healthy, Primary partition).

SO now, I have the following partitions:

sda1 : System reserve
sda2 : Windows C drive
sda3 : Windows D drive
free space (100GiB)

I also made a bootable pen drive with Ubuntu 16.04, and entered BIOS settings to change "boot" modes.

Unchecked legacy mode and set it to UEFI (which means UEFI is supported).

Enabled USB boot-up.

All fine till this stage.

Ubuntu installer opens up, I choose the 'select other option' and choose the unallocated free space, with file system ext4 and mount point as ' /'.

But in the middle of the installation, I get an error which goes:

grub-efi-amd64-signed failed to install into /target/ error

And my installation ceases and a report is sent to Developers

I looked around for solutions; found this:

AskUbuntu : 16.04 new installation gives grub-efi-amd64-signed failed installation /target/ ubuntu 16.04 at the end

NONE OF THE SOLUTIONS WORK.

1) I Have the laptop connected to the internet with secure boot disabled.

2) My file is already named with a '64' in the end

3) I don't know how to create another 200 MiB partition because the max I can have is 4 partitions

4) The same bootable pen drive worked for another laptop (Lenovo Ideapad) - so it's not a pendrive issue

Any Solutions?

I think, (basis of the hours of googling that I have done) that it has something to do with the fact that my memory/disc is MBR and not GPT (although I have no idea what does that mean, other than the fact that I can't create unlimited partitions)

Answer 1

Windows ties the computer's boot mode to its partition table type:

• BIOS/MBR -- Windows insists on a Master Boot Record (MBR) disk when booting in BIOS mode. This was the way most computers booted until late 2011, when manufacturers began shifting to EFI firmware in droves. Newer computers can still boot in this way via a firmware feature called the Compatibility Support Module (CSM), aka legacy-mode boot support.
• EFI/GPT -- The Extensible Firmware Interface (EFI), or its version-2.x variant, the Unified EFI (UEFI), is generally booted from GUID Partition Table (GPT) disks. This is the modern way of booting computers. It has some advantages over BIOS-mode booting, but it's different enough that the learning curve is significant, particularly if you're familiar with BIOS-mode boot tricks, many of which are worthless under EFI.

Importantly, switching between boot modes is usually awkward; it may require changing the boot mode in the firmware on every boot or at least using the computer's built-in boot manager. It's also necessary to create an EFI System Partition (ESP) to hold the EFI boot loader(s), and that is fundamentally the source of your problem -- you don't mention creating an ESP, and I'd wager that's why the installation failed.

Your computer seems to have been booting Windows in BIOS mode from an MBR disk. By booting the Ubuntu installer in EFI mode, you were trying to create a mixed-mode install, with Windows in BIOS mode and Ubuntu in EFI mode (but both booting from an MBR disk). This is the hardest way to install Ubuntu, given your current configuration. In brief, you have three options (well, there are more, but the rest are even more tortuous):

• Install Ubuntu in BIOS mode -- The easiest approach is to install Ubuntu in BIOS/CSM/legacy mode. You can do this by re-enabling the "legacy" option in your firmware that you noted you disabled. If you disabled this option because you couldn't get the installation medium to boot, then chances are that medium was improperly prepared. You may need to adjust options in whatever tool you used to prepare it or switch to another tool entirely.
• Convert Windows to EFI mode and install Ubuntu in EFI mode -- A significantly harder approach, but one you might want to consider if you had a real reason for attempting an EFI-mode install of Ubuntu, is to convert Windows to boot in EFI mode from a GPT disk and then install Ubuntu in that mode. The Microsoft MBR2GPT program is supposed to be able to convert Windows and the disk partitioning system fairly easily; however, I've never used this tool and so I can't comment on it further. Once this conversion is done, Ubuntu should install fairly easily when you boot the installer as you did before.
• Do a mixed-mode install -- In extraordinary cases, a mixed-mode installation makes sense. These circumstances include strange hardware compatibility issues or a need to boot each OS in a particular mode for some reason (say, to write software that relies on one boot mode or the other). You've noted no such reasons. Nonetheless, such an installation is possible. To do it, the key is to create an ESP on your MBR disk. (Although Windows balks at installing to an MBR disk in EFI mode, Ubuntu is more flexible about this.) Once installed, you'll need to learn to control the boot mode, which may involve using the built-in boot manager or even adjusting the boot mode on a boot-by-boot basis in the firmware. My rEFInd boot manager can help in some cases, but you'll need to adjust the configuration: Edit refind.conf, uncomment the scanfor line, and ensure that hdbios is among the options. Note that it can be tricky to get some computers to boot reliably from an MBR disk in EFI mode, so you may need to dig pretty deeply into EFI to figure that out. This is easily the worst of the options unless you have a compelling reason for a cross-boot-mode installation that you haven't mentioned.

Note that the 4-partition limit you mention applies to primary MBR partitions. One of those four primary partitions can be an extended partition, which in turn can hold an arbitrary number of logical partitions. Thus, you can create an ESP (if necessary), a Linux root (/) partition, and as many other partitions as you want, all as logical partitions. Beware, though: The standard Windows partitioning tools flake out when fed extended and logical partitions! Use Linux tools or third-party Windows tools when manipulating disks that use logical partitions. Also, Windows itself must boot from a primary partition. (Ubuntu is not so fussy, fortunately.) The primary/extended/logical partition distinction is unique to MBR; GPT disks do not make this distinction. (Many tools label all GPT partitions as being "primary," simply because the tools were originally written for MBR disks and so require that all partitions be classified as one of those three types.)

Overall, the easiest way to do what you want is probably to do a BIOS-mode install; this will require no conversion of the partition table or potentially disruptive changes to the Windows boot loader; however, booting in EFI mode can be a little faster, and GPT offers some advantages over MBR. (Most importantly, GPT supports disks larger than 2TiB, given a 512-byte sector size.) If you have a good reason for doing it, or if you simply want to experiment, converting Windows to EFI/GPT and installing Ubuntu in EFI mode is worth considering. In the long run, this may be the better option; but the advantages are likely to be modest enough that the short-term risks and time investment is unlikely to be worthwhile.