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November 13th, 2019 07:00
Precision 5540 Laptop: Unable to Boot from UEFI FlashDrive
Recently we had to install a image on a Brand New (Just out of the box) Precision 5540. We were using a UEFI method and booting from a flashdrive. However the laptop was NOT seeing the drive. The machine was seeing the "Windows Boot Manager" and the internal ssd as the two ONLY bootable sources.
After some troubleshooting and several restarts and combing through the bios menu we, seemingly out of options tried deleting the windows boot manager from the list and exiting WITHOUT Saving.
When the computer restarted and we entered the boot menu we saw the flashdrive and when we entered the bios we then saw all three options come up.
SUCCESS!!....
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mawebb
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October 8th, 2020 08:00
Thank you for taking the time for letting us know about this. We were trying to boot to our SCCM boot disk on our new Precision 5540 and wasn't able to get it working until I found this. Thank you so much!
Rodderix
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October 9th, 2020 12:00
Did you try preparing your flashdrive as MBR instead of GPT with Rufus?
jphughan
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October 9th, 2020 13:00
@mawebb and @Rodderix , when booting in UEFI mode, you shouldn't expect to see flash drives in the BIOS Setup. UEFI booting works very differently from Legacy BIOS mode. Whereas BIOS boot options involve devices, a UEFI boot option involves a path to a specific FILE on a specific partition of a specific device. These paths have to be registered in the UEFI firmware. For OSes installed on internal storage, the OS installer handles this. But obviously this sort of registration won't be present for bootloader files on temporarily attached flash drives. This is why in order to boot in UEFI mode from such devices, you should use the one-time boot menu accessed by pressing the F12 button during startup. The options in THAT menu are populated dynamically, not based on registration. The UEFI spec defines a default bootloader file path of \EFI\Boot\Bootx64.efi, so if you have a flash drive connected that has that file at that path, then it will appear in the F12 list, even though it will NOT appear in the BIOS Setup interface. And honestly even with Legacy BIOS booting, the F12 method is much faster anyway since it allows you to override the default boot sequence as needed for temporary situations like this, rather than having to go into the BIOS Setup, rearrange the boot order, and then change it all back when you're finished with your temporary situation.