Switching from UEFI to BIOS/GRUB can be a bit involved. Here's a step-by-step guide to help you convert your

system:

**Warning:** Before making any changes, ensure you have a stable and bootable system with the current

configuration.

**Step 1: Verify your firmware settings**

1. Reboot your system and enter the UEFI firmware settings (usually by pressing **F2**, **F12**, or another key

during boot).

2. Check if the firmware is set to use **Legacy Mode** (also known as **BIOS Compatibility Mode**). If it's already

set, proceed to step 2.

3. Save your changes and exit the UEFI settings.

**Step 2: Update GRUB configuration**

1. Run `sudo update-grub` to regenerate the GRUB configuration file (`/boot/grub/grub.cfg`).

2. This command will detect all available operating systems, kernels, and other parameters.

**Step 3: Update boot loader**

1. You'll need to remove the UEFI-specific entries from your `/etc/fstab` file.

 * Open `/etc/fstab` with a text editor (e.g., `sudo nano /etc/fstab`) and delete any lines related to UEFI bootlo

bootloaders.

2. Update your GRUB configuration by running `sudo update-grub`.

**Step 4: Remove EFI-related packages**

1. You'll need to remove the UEFI-specific packages from your system:

 * Run `sudo emerge -C efibootmgr efivar` (if you installed those packages).

2. This step will help clean up any remaining UEFI-specific configuration files.

**Step 5: Update kernel parameters (optional)**

1. If you've used UEFI-specific kernel parameters, you may need to update them for GRUB.

 * Check `/boot/grub/params` or `/etc/default/grub` for UEFI-specific settings.

**Step 6: Reboot and verify**

1. After completing the above steps, reboot your system to ensure everything is working as expected with GRUB.

2. Verify that you can boot into your Gentoo installation without issues.

If you encounter any problems during this process or need further assistance, feel free to ask!

You're about to enter the build process for your Gentoo system.

**When to update `/etc/fstab`?**

While you can set up your `/etc/fstab` file after completing the build process, it's generally a good idea to do so

before running `make install`. Here's why:

1. **Mount options**: Your system will be configured with default mount options for various file systems (e.g.,

`/boot`, `/home`). You can modify these settings in `/etc/fstab` if needed.

2. **File system layout**: Update your `/etc/fstab` to reflect the actual file system layout, which is created

during the installation process.

Setting up your `/etc/fstab` before running `make install` ensures that:

1. Your system is configured with the correct mount options and file system layout from the beginning.

2. You won't encounter any issues related to incorrect or missing configuration after completing the build process.

**What to do during the build process?**

When you run `make`, it's primarily responsible for compiling your kernel, which doesn't directly interact with

`/etc/fstab`. However, be aware that:

1. **Kernel configuration**: The changes you make in `make menuconfig` will be applied to your kernel

configuration.

2. **File system layout**: Your file system layout will be created during the installation process

(after running `make install`).

**So, what's the best approach?**

To ensure a smooth build process and proper configuration of your Gentoo system:

1. Run `sudo emerge sys-boot/grub` to install GRUB.

2. Create an initial `/etc/fstab` file with default settings or copy it from another system (e.g., your

installation medium).

3. Update the `/etc/fstab` file as needed to reflect your specific setup.

4. Proceed with the build process using `make menuconfig`, `make`, `make modules_install`, and `make install`.

By doing so, you'll have a well-configured system with an up-to-date `/etc/fstab` file that matches your actual

file system layout.

Hope this clarifies things!