Determine Boot Mode and Bootloader

Before proceeding with bootloader configuration, it is crucial to determine the architecture and boot mode of the VM. Let’s clarify this step by step.

Step 1: Determine the Architecture

The architecture of the VM (x86, x86_64, ARM, etc.) can be determined using the following command:

uname -m

If the output is x86_64, the VM is running on a 64-bit x86 architecture.
If the output is i386 or i686, the VM is running on a 32-bit x86 architecture.
Other outputs like aarch64 indicate ARM architecture.

Step 2: Determine the Boot Mode (BIOS vs. UEFI)

The presence of the /boot/loader directory suggests that systemd-boot (formerly gummiboot) might be in use, which is typically associated with UEFI booting. However, since the /boot/efi directory is empty, this could indicate one of the following scenarios:

UEFI Boot with systemd-boot:
- The /boot/loader directory is used by systemd-boot, which is a UEFI bootloader.
- Even if /boot/efi is empty, the UEFI bootloader might be installed elsewhere (e.g., on the EFI System Partition (ESP) mounted at a different location).
Legacy BIOS Boot with GRUB:
- The presence of /boot/grub2 suggests GRUB is being used, which is common for BIOS booting.
- The /boot/loader directory might be a leftover or misconfiguration.

To confirm the boot mode, you can check the following:

Check for UEFI Boot

Run the following command to check if the system is booted in UEFI mode:

ls /sys/firmware/efi

If the directory exists, the system is booted in UEFI mode.
If the directory does not exist, the system is likely booted in BIOS (legacy) mode.

Check for systemd-boot Configuration

If the system is booted in UEFI mode, check if systemd-boot is the active bootloader:

bootctl status

If systemd-boot is installed, this command will display details about the bootloader, including the boot mode (UEFI) and the installed entries.

Step 3: Verify the Bootloader in Use

Based on the above checks, you can determine the bootloader in use:

If UEFI and systemd-boot are confirmed:
- The bootloader is systemd-boot, and the configuration files are located in /boot/loader/entries/.
- You should add your custom kernel entry as a new .conf file in /boot/loader/entries/.
If BIOS and GRUB are confirmed:
- The bootloader is GRUB, and the configuration files are located in /boot/grub2/.
- You should add your custom kernel entry to /etc/grub.d/ and regenerate grub.cfg.

Step 4: Proceed Based on Bootloader

Once you’ve confirmed the bootloader, you can proceed as follows:

For systemd-boot (UEFI)

Create a new .conf file in /boot/loader/entries/:

sudo nano /boot/loader/entries/copied_kernel.conf

Add the following content (adjust paths as needed):

title Copied Kernel
version Copied Kernel
linux /boot/copied_kernel/vmlinuz-copied
initrd /boot/copied_kernel/initrd.img-copied
options root=/dev/sda1

Reboot the system, and the new entry should appear in the boot menu.

For GRUB (BIOS)

Create a custom entry in /etc/grub.d/:
```
sudo nano /etc/grub.d/40_custom
```

Add the following content (adjust paths as needed):

menuentry 'Copied Kernel' {
    set root='hd0,msdos1'
    linux /boot/copied_kernel/vmlinuz-copied root=/dev/sda1
    initrd /boot/copied_kernel/initrd.img-copied
}

Make the file executable:
```
sudo chmod +x /etc/grub.d/40_custom
```

Regenerate the GRUB configuration:

sudo grub2-mkconfig -o /boot/grub2/grub.cfg

Reboot the system, and the new entry should appear in the GRUB menu.

Summary of Steps

Determine the architecture using uname -m.
Check the boot mode using ls /sys/firmware/efi and bootctl status.
Verify the bootloader (systemd-boot or GRUB).
Add the custom kernel entry based on the bootloader.