Thanks for the info.
Can anyone explain why switching to legacy boot is necessary?
I'm putting together a custom Ubuntu installation image for the DN2820FYKH, and I'm having trouble getting an install process that will work on all of our NUCs.
The problem I'm seeing is that an install done on one NUC may or may not work if I swap the disk into another - sometimes I get the "no bootable disk found" message (I don't remember the exact wording). I need to have one image that will work on all the NUCs so I can do an install onto one disk and run it through a disk duplicator. I've got some NUCs with BIOS version 015 and some with 032, I'm upgrading them all to 047 but the 015's need two installs to get both the BIOS and the BIOS config installed, so there's a chance that something's not getting updated correctly. I'm trying to come up with a matrix of what works and what doesn't, but it's a confusing and time consuming process, so I'm hoping that someone else has fought this battle already.
I need UEFI boot, so I can't just switch to legacy boot.
Encouraged by this thread, I went through all available BIOS versions on the support download page for the DE3815TYKHE (D3815TYBE). Currently, they are 19, 24, 30, 32, 34, 36, 37, 39, 41. I did not test 19 as I could not access the internal eMMC using it. I used the iflash from DOS method of flashing as the others I tried (update from boot screen, update/recover from hold-power-button-four-seconds screen, and recover by removing BIOS security jumper) proved unreliable and failed for no apparent reasons in different stages of the process.
Of all tested versions, only version 24 of the DE3815TYKHE BIOS allowed me to boot without a display connected, and to connect a VGA display to the NUC after the boot and get a picture, if needed. The only change from the default BIOS settings I had to make was to enable the eMMC boot device (and set OS selection to Linux). I did not disable UEFI.
The BIOS versions for the DE3815TYKHE and DN2880FYKH released after the working versions (30 and 37, respectively) were both released on the same date: 2014-07-10. If this issue affects other NUCs as well, I would imagine trying BIOS versions prior to this date would be a good place to start.
So headless boot was working but something Intel did in July of last year broke it.
To be clear, this is a non-GUI Debian 7.8 installation and the issue is booting without a display connected. As far as I know, then, this issue is not related to the remote desktop/VNC problems that one can't help but notice when searching for solutions in this forum. But perhaps in attempting to solve that problem, Intel changed something that broke something else.
The issue is not resolved but at least I now have a workaround. Thanks, thread starter. Intel, you're up.
(As an aside, I am disappointed in Intel. I've spent many hours on this ridiculous issue, which is exactly what I expected not to have to do with an Intel product and why I went with Intel rather than Gigabyte or another competitor with similar but cheaper products.)
Using DN2820FYKH, with the last bios 0048.
For me it was enough to check the Legacy Boot - without unchecking UEFI Boot, and everything boots without monitor attached. It did not work without Legacy boot checked.
Installed Debian Wheezy for UEFI Boot.
Bios 0034 also worked with the same condition.
Thanks for your note!