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I have a Windows installed on my HDD drive. I bought a SSD and installed Ubuntu on it as it's described in this question answer and partitioned it as it says in this question answer (on sdb of course). But in the first one it says that after installation there would be an option to choose OS:

So open BIOS, change boot disk priority so that the disk containing Ubuntu comes first.

This time, GRUB will be loaded. And you can boot either OS.

But when I choose my Ubuntu as first disk to boot in the Gigabyte UEFI, it doesn't let me choose between Windows and Ubuntu. I didn't install GRUB manually because I thought it will come with Ubuntu installation. And only after some research I realized that I need to install GRUB manually, is it correct? After installation I checked that my SSD is MBR, while my HDD is GPT. I didn't do anything with SSD except creating partitioning while installing Ubuntu.
I checked UEFI, when I was installing option Storage boot option control was set to Legacy and Other PCI devices option was set to UEFI. Right now, after installation, If I change first one to "UEFI" it just starts to name my SSD correctly, containing "SSD" in the name, while in "legacy" it just repeats the name of the HDD where Windows is installed, but without containing "(windows boot)" at the end or something like that, but in both cases it boots my Ubuntu and Windows correctly (in the order I place them).
So my question is, what should I do now? Did I do something crucial bad and need to re-install Ubuntu completely? If it can be fixed, what exactly steps I need to do in order to get to choose which system to boot at the start? Thanks in advance.

Arzybek
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  • The first Q&A you mention is hopelessly outdated. Relevant in the context of BIOS (the majority of machines had BIOS when the question was posted) but no longer relevant 10 years after with UEFI. It's not that you need to reinstall Ubuntu but that is actually the faster and less error prone option. Please check the follow up comment (duplicate flag) which is about what you need to know for a Windows-Ubuntu dual-boot in UEFI systems. – ChanganAuto Feb 01 '22 at 13:28
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    Does this answer your question? How do I install Ubuntu alongside a pre-installed Windows with UEFI? – ChanganAuto Feb 01 '22 at 13:28
  • You need to install Ubuntu in UEFI mode. Boot the installation USB in UEFI mode. – user68186 Feb 01 '22 at 13:29
  • See this answer for how to boot in UEFI mode. – user68186 Feb 01 '22 at 13:37
  • @ChanganAuto, thanks, can you clarify one moment for me please, do I have to install GRUB manually or it will be installed automatically with Ubuntu in UEFI installation? – Arzybek Feb 01 '22 at 14:26
  • Automatically installed either way. Need to know: How it boots is how it installs. So, you need to boot in UEFI mode because your preinstalled Windows is in UEFI mode (since Windows 8 in 2012). Make sure Fast Startup in Windows is disabled first. Ubuntu then will be installed to the select drive with automatic (uses the existing ESP by default) or manual partitioning (the ESP needs to be selected). – ChanganAuto Feb 01 '22 at 14:40
  • Read these two similar questions and answers for a better understanding 1. Dual Booting win 10 and Ubuntu 18.04 on two separate physical ssds and 2. How do I uninstall/reinstall Ubuntu on HDD from separate OS (Windows 10 operating on SSD)? – user68186 Feb 01 '22 at 15:12
  • UEFI and BIOS are not compatible. You want to convert SSD to gpt now before its too late. The only place MBR should still be used is for 10 year old BIOS installs of Windows. Conversion from MBR to gpt will erase drive, so if you already have data, be sure to back it up. UEFI/gpt partitioning in Advance, new versions use swap file so swap partition optional: http://askubuntu.com/questions/743095/how-to-prepare-a-disk-on-an-efi-based-pc-for-ubuntu How you boot install media UEFI or BIOS is then how it installs. And now that drive is MBR, it may install UEFI but using old MBR. – oldfred Feb 01 '22 at 18:28

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