Shell W101

0 views

Skip to first unread message

Alayna Rother

unread,

Aug 3, 2024, 4:37:26 PM8/3/24

to duihybcioroc

Slip into the Olympia Softshell pants this winter and embrace the outdoors. From skiing to nature hikes, the high rise and boot leg snow pants are crafted with a contoured waistband. Complete with center front zipper opening and back elastic insert, they come with two lateral zip pockets, inner gaiters with elastic gripper and back leg exposed zip openings.

I am using an embedded board that supports UEFI. It is a new fangled board and comes up with American Megatrends BIOS and a UEFI shell (I am more used to dealing with a bootloader and not a PC BIOS on an embedded board).

I would like to write a script to make the BIOS Shell do this. If the machine is hosed and we have corrupted the bootsector on a deployed system, I would like to automatically run a restore sequence. Is this sort of thing possible? Can I do it with a UEFI shell? Is this doable in anyway?

EFI doesn't use the boot sector of the disk. Thus, I suspect that you misunderstand what's happening to your system. My guess is that you're actually damaging the NVRAM entries that hold the boot order for the device. The easiest way to deal with this problem is to not use those entries, and instead name your EFI boot loader EFI/BOOT/bootx64.efi (or more generally, bootarch.efi, where arch is an architecture code; x64 is the architecture code for x86-64). If you don't want to do this for some reason, and if your EFI shell is a version 2 shell, you can use the bcfg command in an EFI shell script to do the job. This command is documented to varying extents in various places, such as the Arch Linux wiki and Intel's site. Unfortunately, the older version 1 EFI shell doesn't support the bcfg command, so this option won't work with it, although it might be possible to extract the relevant code from the TianoCore source code and create a standalone bcfg command that you could use with an older shell.

If you really need to write to the MBR, then writing an EFI application in C might be a better choice than trying to do it in the EFI shell. There's a lot of EFI programming documentation out there, but most of it is like Unix man pages -- it assumes that you already know the topic and just need to check the details. I've written a brief tutorial introduction, but it's very basic and doesn't cover disk I/O. (You could use that and the source code to gptsync, which is included in the last couple versions of rEFInd, though, to learn how to read and write the MBR of a disk.)

If I understand correctly, whatever you do (unless using the fallback filename is sufficient), you'd need to fit it into the normal boot sequence. This would be possible with either an EFI shell program launched as the default or as a binary program; but you'll have to be sure that your custom program concludes by launching the "real" boot loader, or that the "real" boot loader launches after the new program.

Indeed, the shell is found in the basement. Square did a great job with the pacing of this quest, cutting back and forth between the trial upstairs and the frantic (if easy-as-anything) race in the basement.

Turns out that, yup, it was definitely a frame-up. The chancellor was a descendant of the fake chancellor from 600 AD and out for some old fashioned revenge. This goes about as well for him as it did for his ancestor the first time.

If you have completed downloading and installing a Windows update, your tablet might boot into the EFI shell instead of Windows. This issue can occur as well randomly on occasion but the most common cause is the installation of the Microsoft Windows 1709 Fall Creator Update and the boot order has been changed.

We may request cookies to be set on your device. We use cookies to let us know when you visit our websites, how you interact with us, to enrich your user experience, and to customize your relationship with our website.

Click on the different category headings to find out more. You can also change some of your preferences. Note that blocking some types of cookies may impact your experience on our websites and the services we are able to offer.

Because these cookies are strictly necessary to deliver the website, you cannot refuse them without impacting how our site functions. You can block or delete them by changing your browser settings and force blocking all cookies on this website.

These cookies collect information that is used either in aggregate form to help us understand how our website is being used or how effective our marketing campaigns are, or to help us customize our website and application for you in order to enhance your experience.

We also use different external services like Google Webfonts, Google Maps and external Video providers. Since these providers may collect personal data like your IP address we allow you to block them here. Please be aware that this might heavily reduce the functionality and appearance of our site. Changes will take effect once you reload the page.

We may process your Personal Information for carefully considered and specific purposes which are in our and in your Legitimate Interest. Learn More about how we work for compliance with the General Data Protection Regulation (GDPR).