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.