Hello again!
first some good news: I moved a step forward.
Booting from USB CDRom is possible!
One must enter UEFI/Bios Menue -> Advanced -> USB Features -> Legacy USB Support [enabled]. Then a bootable CDRom starts.
BTW: Is that feature documented, anyhow? It would have saved a lot of time, if I had known it.
Now, I can boot again from an certain, single USB stick. After booting a Linux from a CDRom, I could create a boot entry for my USB boot stick (exactly for a particular stick, not general for any bootable USB sticks).
In efibootmgr, now it looks like this:
Code: Select all
BootCurrent: 0002
Timeout: 0 seconds
BootOrder: 0002,0001,3010,3000,300E,3002,3003,300A,0000,2001,2002,2003
Boot0000* Windows Boot Manager HD(1,GPT,d51839a0-d358-4337-a3a8-0c8a8093928c,0x800,0x200000)/File(\EFI\Microsoft\Boot\bootmgfw.efi)57494e444f5753000100000088000000780000004200430044004f0042004a004500430054003d007b00390064006500610038003600320063002d0035006300640064002d0034006500370030002d0061006300630031002d006600330032006200330034003400640034003700390035007d000000ffff0100000010000000040000007fff0400
Boot0001* GRUB HD(1,GPT,feb7f071-3733-4764-a7a9-64afb0418311,0x800,0xb8c800)/File(\EFI\GRUB\grubx64.efi)
Boot0002* sda arch HD(1,GPT,feb7f071-3733-4764-a7a9-64afb0418311,0x800,0xb8c800)/File(\EFI\BOOT\BOOTX64.EFI)
Boot2001* EFI USB Device RC
Boot2002* EFI DVD/CDROM RC
Boot2003* EFI Network RC
Boot3000* Floppy Disk Drive: FJ
Boot3002* Drive1 HDD: FJ
Boot3003* Drive2 HDD: FJ
Boot300A* Drive3 NVMe: FJ
Boot300E* NETWORK: FJ
Boot300F* USB HDD: FJ
Boot3010* USB CD/DVD: FJ
In total, I am seeing 13 boot items.
Boot0001 and Boot0002 are created with help of efibootmgr. They are related to an USB stick with a certain UUID, a certain path to an EFI file, etc. So they won't boot any bootable USB stick, only the certain, matching one.
Formerly, any bootable USB stick could be booted by "Boot300F USB HDD". efibootmgr still shows this entry, but in UEFI/Bios menue (F2) I have only this:
-> Boot300F is missing!
With efiboormgr I can add Boot300F to the boot order, but this setting is not permanent. The entry disappears again for unknown reasons from the boor order
I need this entry or an entry similar to it for booting from any bootable USB stick, not only from one particular device.
Any hints, how I can recover/repair this boot entry?