Arch Linux

jxyzits

Member

Registered: 2016-07-25

Posts: 3

[SOLVED] Boot goes to BIOS after modifying boot entry with efibootmgr

Well, I feel like an idiot. I normally boot in UEFI mode and this has been working fine for months, I had X running for a while, the whole nine yards. Today I was trying to fix my tty display resolution and decided to try adding a "video=1920x1080" kernel option to the end of my default boot entry using efibootmgr. I reboot and I only get to BIOS with no obvious ways of launching a recovery shell or anything like that. There is a BIOS option to "Launch EFI Shell from filesystem device" (Shellx64.efi) but this just returns with a "WARNING: Not Found."

I am assuming that the way to fix this is to run efibootmgr again and set my boot entry back to what it originally was (or edit the boot entry in whatever file it is stored in, if any), but I don't know how to get to a shell. How can I go about doing this? I think what I need to do is burn an Arch ISO to an EFI-bootable USB drive and boot from it, mount my drive/partitions, chroot in, and run efibootmgr there. I just hope this will cause efibootmgr to update the boot entry on my hard drive rather than the USB drive - this is what I'm not sure on and am asking for help for.

If it matters, my computer has a single drive, sda, which has a FAT32 /boot partition containing the ESP. The rest of my partitions (/ included) are in an LV spanning the rest of the disk. I have USB flash drives and CDs on hand should I need to create a recovery media. Any help is appreciated.

EDIT: Am I correct in assuming that the kernel options are stored in plaintext in ${esp}/loader/entries/${entry}.conf?

EDIT2: I should add I don't use a separate bootloader, I boot directly from the EFISTUB.

Last edited by jxyzits (2016-07-28 03:43:22)

Head_on_a_Stick

Member

From: London

Registered: 2014-02-20

Posts: 7,732

Website

Re: [SOLVED] Boot goes to BIOS after modifying boot entry with efibootmgr

I am assuming that the way to fix this is to run efibootmgr again and set my boot entry back to what it originally was (or edit the boot entry in whatever file it is stored in, if any), but I don't know how to get to a shell. How can I go about doing this? I think what I need to do is burn an Arch ISO to an EFI-bootable USB drive and boot from it, mount my drive/partitions, chroot in, and run efibootmgr there.

You don't need to mount your filesystems or use `arch-chroot` -- the `efibootmgr` command works on the motherboard and so can be run from any live environment.

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Are you infected with Wetiko?

jxyzits

Member

Registered: 2016-07-25

Posts: 3

Re: [SOLVED] Boot goes to BIOS after modifying boot entry with efibootmgr

Thanks Head_on_a_Stick, that solved it. I can now boot again without an external boot media.