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Alber

Member

From: Spain - España

Registered: 2011-11-11

Posts: 227

[Solved] systemd-boot, what is this entry: /boot/4f5d53... (a hash?)

Hello.

I'm installing arch in a USB (in a laptop with windows), and when install systemd-boot it creates a random dir (maybe it's a hash or a random seed) and a default entry in loader.conf with the same number.

By example, when it boots from the USB, which have a own EFI partitions. It must use the default entry in /boot/loader/loader.conf.
The boot used:

# efibootmgr -v
BootCurrent: 000C
boot000C* Linux Boot Manager HD(1,GPT,2e0.....)/File(\EFI\systemd\systemd-bootx64.efi)

There is a dir in /boot

/boot/4f5d53....

and an entry in /boot/loader/loader.conf

default 4f5d53....-*

maybe it is related to a start message that says:

sha256 validated
Failed to acquire RNG protocol: not found

Someone knows what is this dir and entry? Or a idea of where to search.

Thankyou

edit: added some explanations.

Last edited by Alber (2019-09-22 18:56:43)

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Because not all of us are native English speakers, try no to use slang or abbreviations, thank you.

V1del

Forum Moderator

Registered: 2012-10-16

Posts: 25,412

Re: [Solved] systemd-boot, what is this entry: /boot/4f5d53... (a hash?)

https://github.com/systemd/systemd/blob … #L401-L430

Last edited by V1del (2019-09-19 07:10:36)

Alber

Member

From: Spain - España

Registered: 2011-11-11

Posts: 227

Re: [Solved] systemd-boot, what is this entry: /boot/4f5d53... (a hash?)

Following the link provided by V1del, in its text, there is another:
    https://systemd.io/RANDOM_SEEDS

I haven't had time to read it all. So what I'm going to tell my be wrong:
There is an initial seed placed in the file /loader/random-seed. OK, I've this file. And there is another token in NVRAM. When systemd-boot boots, both are used to generate a new seed (which is stored in /loader/random-seed, I suppose) and to pass it to the Kernel, too.

Changing the subject
Because I have the next thinking:
  If the directory's name /boot/4f5d53.... is in an entry in the loader.conf, so it must related with some EFI app.

default 4f5d53....-*

I don't know what mean -* chars at the end.
I've made some tests.
If I do the sha256sum from EFI file /boot/EFI/systemd/systemd-bootx64.efi and it matches with the name of the directory.

# sha256sum /boot/EFI/systemd/systemd-bootx64.efi
4f5d53....

# ls -l /boot
drwx----- ....   4f5d53....
drwx----- ....   EFI
-rwx----- ....   initramfs-linux.img
...... 

So it looks like as a default behavior:
  If there is a default entry which is not in /boot/loader/entries try with the default (or defaults) EFI apps, /boot/EFI/systemd/systemd-bootx64.efi, and boot if sha256sum match.
  I don't know by it could be this way.

In case someone wants to contribute with something more, I will wait a time before mark the thread as [solved]

Edit:
  Now I thinking that /boot/EFI/systemd/systemd-bootx64.efi is himself (systemd-boot). Not a Linux efi boot stub. And just try to load an initramfs-linux.img to launch a Linux system.

  # efibootmgr -v
BootCurrent: 000C
boot000C* Linux Boot Manager HD(1,GPT,2e0.....)/File(\EFI\systemd\systemd-bootx64.efi)

Last edited by Alber (2019-09-19 18:41:18)

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Because not all of us are native English speakers, try no to use slang or abbreviations, thank you.