# Thinkpad T420 UEFI not writable

## sDoky

Hi guys ... I have a problem with my thinkpad. It seems not to be able to write any UEFI changes I try to do via efibootmgr. I cannot access the boot select F12 menu, the F1 startup menu or anything for that matter. I thought of disconnecting the BIOS battery for a minute, but there's possibility, that I couldn't boot anything at all. I realized this issue while adding new kernel to uefi memory and the efibootmgr didn't give any warning at all, just didn't make any changes. Is this the time for warranty repair (I do not thing they're gonna like seeing linux there) or is there any way of repairing the memory or whatever from inside my linux? Has any of you experienced this issue earlier?

Thank you

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## Logicien

Hello,

is Windows already install? I assume yes. Which bootloader have you install for Gentoo? Do you mean you cannot access the EFI/BIOS keys F12 and F1 since you install Gentoo in EFI mode or the problem was before? I assume since Gentoo.

I ever remove the EFI/BIOS battery. You will loose the EFI/BIOS setup and menu configuration. they will be reset to default. After that, I had to put a bootable cd/dvd to access the boot menu with the associated key. You can try that before remove the battery.

I had to reconfigure the EFI/BIOS setup and menu. Using the UEFI Shell give me better result than efibootmgr. But I have not been able with those tools to change the Windows EFI bootloader as the default of the EFI/BIOS menu. The subject Dual-boot with Win8 on UEFI can help you for that.Last edited by Logicien on Sun Jun 30, 2013 2:18 pm; edited 2 times in total

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## Hu

OP: have you previously used efibootmgr successfully and now found it not to work?  If so, your UEFI implementation may be refusing the change.  This can happen if it has too little free space in the UEFI variable store.  If I recall correctly, efibootmgr error reporting is quite poor, so you might not get any output when it fails.

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## srs5694

Two more points:

There have been problems reported lately with certain combinations of specific versions of efibootmgr with specific versions of the Linux kernel. I don't recall the details of what doesn't work with what, but upgrading one or both might help; or you could use "bcfg" from an EFI version 2 shell (as Logicien has suggested; see his links) or "bcdedit" from Windows. Note, however, that passing options from these tools might be difficult or impossible, so you might need to use a third-party boot manager, like gummiboot or rEFInd.

Some firmware bugs can be fixed by upgrading the firmware. Check with the manufacturer to see if any are available for your computer, and if so, apply the update.

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## sDoky

Thank you for your replies.

It used to work okay. I used to add and remove items via efibootmgr on regular basis

I do not use any loader. I just compile kernel as "EFI Stub" and load it directly via UEFI

Windows is installed, but I cannot select it to boot

I cannot boot anything except my Gentoo Linux 3.8.5 kernel located at the first fat32 partition (for EFI to find)

I do not have EFI shell installed at all

I suppose bios update can be performed exclusively from windows

There's only one version in portage, which is the one I use

I am not sure I have any Lenovo bootable CD. I can look for the box it came in, but I'm not sure where it is

Can I use any bootable CD, or does it have to be some particular one?

Can any of you share bit copy of the CD so that I could burn it?

What are my options?

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## srs5694

You can place an EFI shell or boot manager program on a USB flash drive to use it. Give it a name of EFI/BOOT/bootx64.efi on a FAT filesystem, preferably with the ESP filesystem type code set ("EF00" in gdisk, or via the "boot flag" in parted-based tools). In fact, rEFInd is available as a bootable USB flash drive or CD-R image, and that version ships with an EFI shell (version 2 for x86-64), so you can use that if you like.

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