UEFI and linux

I recently mentioned that I had purchased a Windows 8 box.  One of the things that will do, is give me an opportunity to work with UEFI systems.  And what I have learned, thus far, is that things are rather unsettled when it comes to UEFI and linux.

I am currently looking at the web page “Managing EFI Boot Loaders for Linux” which is giving me some insight into the situation.  While I cannot vouch for the accuracy of everything in that web page, it at least seems to be consistent with what I am reading elsewhere.

What I have tried

I’ll note that the UEFI box is a Dell.  I can access the BIOS settings by hitting F2 during boot.  Or I can access the boot menu by hitting F12 during boot.

Here’s what I have already tried with the UEFI box.

I inserted a bootable CD, then hit F12 during boot.  The box booted straight into Windows with no options.

I next rebooted, and hit F2 to get into the BIOS settings.  And there, I disabled secure boot.

Back to using a bootable CD, I hit F12 and was presented with a boot menu.  The menu listed UEFI boots (only Windows), and MBR boots (both the hard drive and the inserted CD).  I booted from the CD.

Since then, I have added a second hard drive, where I eventually plan to install linux.  I first used a disk enclosure so that I could access the new hard drive as a USB external drive.  Connecting that to my current system (opensuse 12.3 RC1), I use “gdisk” (the “fdisk” variant for gpt partitioning), and created a gpt partition structure.  After that, I installed the new hard drive in the UEFI box.  Windows 8 sees it as having a protective partition and a lot of unallocated space.

Next, I booted from a USB with the opensuse 12.3 RC1 DVD image (64 bit).  This required hitting F12 during boot.  Only Windows showed up as a UEFI boot, with my install USB showing up as an MBR boot.  The opensuse installer wanted to install in MBR mode.  I aborted the install.

I next tried the Fedora live 64bit CD iso (on a USB).  Again, hitting F12 while booting, this showed up as a UEFI boot.  Once booted, I clicked the option to install Fedora.  And that wanted to do an EFI install.  I was not intending to install at that point.  I was only testing.  So I aborted that install also.

Here’s what’s strange

According to the Fedora documentation, you must install from a DVD or CD.  Alternatively, if you want to install from a USB, some special USB preparation steps are given.  I had used a USB without those special preparation steps.  I had just used “dd” (really, “dd_rescue”) for a raw copy of the iso to the USB device.  And it booted into UEFI mode.

Back on my computer, if I use

fdisk -l iso-file-name

on the Fedora iso file (either the 64 bit KDE live or the 64 bit DVD image), it tells me that there is a gpt partition table there.  So I was not at all surprised that it booted in UEFI mode.  The same check of the opensuse iso did not indicate a gpt partition table, so I was not surprised that failed to boot into UEFI mode.  Note that “gpt” and “UEFI” are not the same thing.  However, if somebody went to the trouble of providing a gpt structure on the iso, it is likely that they wanted to use that with a UEFI boot.

It is my understanding, perhaps mistaken, that if I write the opensuse image to an actual DVD, then I will be able to boot it in UEFI mode.  I’ll probably wait for the final release of 12.3 before testing that.  At this point, I am unclear on what is required of a DVD, for it to boot in UEFI mode.

That’s the state of what I currently know.  I’m treating this as a learning experience.  Long term, UEFI should be a better way of booting.  For now, the situation is murky.

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About Neil Rickert

Retired mathematician and computer scientist who dabbles in cognitive science.

4 responses to “UEFI and linux”

  1. youngpenguin says :

    On my HP box, openSUSE 12.2 boots fine with EFI from DVD, same as Fedora!! 😀

    Like

    • Neil Rickert says :

      Thanks.

      Yes, it is my expectation that the DVD would boot to UEFI mode. There are bug reports for UEFI booting of 12.3 RC1, so I’ll wait. The final release should be available soon, so I might as well wait.

      What does not work, in my tests, is UEFI boot of the DVD image written to a USB. I have tried my 12.2 USB and my 12.3RC1 USB, and both boot only in MBR mode. However, Fedora 18 boots okay in UEFI mode from a USB.

      Thanks for your feedback.

      Like

  2. youngpenguin says :

    Ah, right. 🙂

    Like

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  1. UEFI booting – basic concepts | Thoughts on computing - 2013/03/02

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