[Solved] Need guidance about efi partition.

[gardenair]

hi,
I am facing an ambiguity and want to learn about (UEFI systems) /efi and /boot/efi ,
So installing Gentoo for a laptop corei7 9th Generation what is the best practice for efi setup in partition ?

If I follow Gentoo handbook https://wiki.gentoo.org/wiki/Handbook:AMD64/Installation/Base#Preparing_for_a_bootloader here it shows

[pietinger]

gardenair,

you will need only one ESP (efi system partition). This partition must be formatted with a FAT variant (recommended FAT32). Before September 2023 this partition was mounted to /boot. Then it was changed und a new mountpoint was created: /efi ... Today you mount your ESP to /efi and install according to our handbook. /boot/efi ist outdated ... dont use it.

See more here:
https://wiki.gentoo.org/wiki/User:Pietinger/Draft/Quick_Installation_OpenRC_for_an_UEFI_System

In this article you will get an overview about UEFI booting (dont use it; it is only for a manual configured kernel): read only chapter: "Prerequisites for an UEFI boot"
https://wiki.gentoo.org/wiki/User:Pietinger/Tutorials/Boot_kernel_via_UEFI
In this article you will find also a link to:
https://forums.gentoo.org/viewtopic-t-1165115-highlight-.html
_________________
https://wiki.gentoo.org/wiki/User:Pietinger

[logrusx]

[NeddySeagoon]

gardenair,

Mount points and partitions are fairly separate but related concepts.
In what follows they are not related at all.

First some definitions
Partitions exist on block storage devices.
Mount points are locations in the kernel filesystem tree where filesystems, often but not always, contained an partitions may be mounted.
Mount points only exist after the kernel has started. That's important. The EFI firmware has no concept of mount points. It does not need one.

When the EFI firmware starts it does some checks then reads the partition table to find the EFI System Partition.
You may have several EFI System Partitions but don't. It will make your head hurt.
From the ./EFI directory in the EFI System Partition, the EFI firmware will load an EFI compliant program.
That can be anything. An EFI stub kernel, a boot loader ... whatever.
The firmware does this all on its own. The kernel is not yet leaded so there are no mount points yet.

Whatever gets loaded, it has to bring up the system all on its own. Calls to the EFI FIrmware are possible, but its the EFI compliant program in RAM in control.

Lets say that its a boot loader like grub.
Grub will load the rest of itself and show a menu which you interact with to load the kernel and initrd of your choosing.
There is still no filesystem tree yet.

When the kernel starts, it is told where to find the root of the filesystem tree with root=... on the kernel command line.
Once root is mounted the filesystem tree and mount points begin to exist.
The localmount service attaches more filesystems (not partitions) to the tree.

Several things follow from this.
1. The EFI System Partition need only ever mounted in the kernel filesystem tree when its contents need to be changed.
2. As long as you know where it is, it can be a different place every time.
3. The concept of a location in the kernel filesystem tree for the EFI System Partition is only a user convenience. Its the user that maintains the mapping, The system does not mind, hence my opening

[sMueggli]

The ESP is always a FAT formatted partition.

Whether you mount it to /efi or /boot/efi is your choice. If you choose Grub as a bootloader then about 99% of the guides in the internet are expecting the ESP mounted to /boot/efi (, because this is the Grub-default). If you follow the Gentoo way and you like to blindly follow instructions, you will use /efi as mountpoint (and you have to remember that you mounted the ESP to /efi and not /boot/efi). If you follow the Gentoo way and you know, what you are doing, then you can do what you want.

Using either /efi or /boot/efi, you do not need a separate /boot-partition. But if you have a separate /boot-partition and you choose /boot/efi as mountpoint for the ESP, then you need to mount first /boot and afterwards /boot/efi (you have a nested mounts and the order is important).

[gardenair]

Thanks all for the detailed reply. Appreciate it. The topic is itself a book.