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Edited (0a01f13) at 2020-10-03 by Dylan Araps
EFISTUB [0]
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The Linux kernel has the ability to act as an EFI executable which simplifies
the boot process by removing the need for a bootloader.
Prerequisites
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Begin by first verifying that you have efibootmgr installed:
+------------------------------------------------------------------------------+
| |
| $ kiss b efibootmgr && kiss i efibootmgr |
| |
+------------------------------------------------------------------------------+
The kernel must be configured to support acting as an EFISTUB.
+------------------------------------------------------------------------------+
| |
| CONFIG_EFI_STUB=y |
| |
+------------------------------------------------------------------------------+
The UEFI variables must be mounted.
See: @/efivarfs
+------------------------------------------------------------------------------+
| |
| TIP: Keep your kernel's name as 'vmlinuz' to avoid having to update the |
| EFI entries with each kernel update. |
| |
+------------------------------------------------------------------------------+
Create an UEFI boot entry
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Use the following command to create a boot entry. Replace /dev/sdXN with your
EFI system partition and /dev/sdYM with your root partition. Check to see that
the entry was added with 'efibootmgr --verbose'.
+------------------------------------------------------------------------------+
| |
| $ efibootmgr \ |
| --create \ |
| --disk /dev/sdX \ |
| --part N \ |
| --label KISS \ |
| --loader /vmlinuz \ |
| --unicode 'root=/dev/sdYM' \ |
| --verbose |
| |
+------------------------------------------------------------------------------+
The root partition can also be referred to by its partition UUID which can be
found using blkid.
+------------------------------------------------------------------------------+
| |
| --unicode 'root=PARTUUID=aaaaaaaa-aaaa-4aaa-aaa-aaaaaaaaaaaa' |
| |
+------------------------------------------------------------------------------+
The above command, the --unicode option specifies the parameters passed to the
kernel. If you require other parameters to boot your system, pass them here.
Removing a UEFI boot entry
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To remove an entry, find your entry's boot number using 'efibootmgr --verbose'
and run the following command.
+------------------------------------------------------------------------------+
| |
| $ efibootmgr --bootnum XXXX --delete-bootnum |
| |
+------------------------------------------------------------------------------+
References
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[0] https://www.kernel.org/doc/Documentation/efi-stub.txt
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Dylan Araps (C) 2019-2020
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