I apologize for the length of this post. I wanted to be as detailed as I could. Also, I tried everything from this link: My computer boots to a black screen, what options do I have to fix it? and it didn't help.
First here's some background: A few days ago I successfully installed ubuntu 15.10 on my toshiba satillite c855d-s100, which has 4gb ram and an amd processor (I can't give you more details at the moment because I can't get into it).
At first I was having some trouble getting the live cd to run, but I fixed it by going into bios and enabling secure boot (I read that secure boot had to be disabled, but I couldn't boot the live cd until I enabled secure boot). Anyway, after I did that, I was able to successfully run the live cd and install ubuntu 15.10 on the laptop.
At first I had no problems. I was able to run ubuntu and reboot it several times without any issues, except that "ignoring bgrt" would appear on my screen for a split second before loading but otherwise ubuntu ran fine.
So now here's the problem: Last night I rebooted the laptop and after selecting ubuntu in the grub, the laptop booted to a blank purple screen. I let it sit there for 30 minutes and nothing changed.
I tried adding nomodeset to the grub and the same thing happened. Sometimes it's a purple screen, sometimes it gets frozen at "ignoring bgrt" and stays stuck there. I tried putting nomodeset in front of quiet splash, I tried deleting quiet splash and adding nomodeset, I have tried putting nomodeset in between quiet and splash. Sometimes I get past 'ignoring bgrt' and see a string of text that ends with "wmi: mapper loaded" but it freezes there.
I have also tried adding radeon.modeset=0 with the same results. I also tried adding either nomodeset or radeon.modeset=0 to the gfxmode line and got the"wmi mapper loaded" screen. I even tried deleting the gfxmode line completely and got nothing.
I tried going into bios and disabling secure boot, but that leads to the same results as above.
I have tried clicking on advanced options in grub and booting in recovery mode, but I get the black screen with a string of text that ends with "wmi: mapper loaded" and freezes there. Also in the advanced options screen I tried to boot using a different kernal, but that froze at "loading initial ramdisk"
I have tried running the live cd again, both with secure boot disabled and enabled, and I get to the grub that says "try ubuntu without installing" but I get frozen at the same "ignoring bgrt screen" again when I click on it
Does anyone have any ideas?
Am I using nomodeset and the other commands wrong? Here is what the linux line in the 'edit grub' screen says:
/boot/vmlinuz-4.2.0-34-generic.efi.signed root=UUID=c0e7414a-8d97-43c8-b9fb-0d1994fa5452 ro quiet splash $vt_handoff
I described above all the ways I've added nomodeset and radeon.modeset=0 to that line.
I have also tried adding nolapic with no effect. I also tried adding acpi=off and that led to a screen that had a string of text that ended with "switching to radeondrmfb from EFI VGA" where it then froze.
What else can I do? I just don't get it. Ubuntu itself was working perfectly for two days and now this.
Update: Now I've somehow managed to accidently wipe out the grub completely and the laptop boots directly into windows. And since I can't get the live CD to work anymore as described above, I can't do anything about that either.
For now, unless there's another solution other than what I've already tried, I think I'll just use that laptop to store my backups on the windows partition (I don't want to go back to using windows in my daily life, I love ubuntu) and just switch to my spare laptop, which has had ubuntu on it for months, and use that as my main laptop from now on.
