Fresh install Grub2 weirdness

Punchcutter · Guru Joined: 11 Feb 2007 Posts: 354

Hi... I hope this makes sense - I'm gonna try to keep it easy to follow:

Have a fresh install. Using Grub2 (for the 1st time). Booting generally seems to be fine.

During the install, I used genkernel to make the first kernel, although I always edit later to remove all the excess crud and tune things for my own needs.

Following the usual install instructions, I got a grub setup with a kernel AND an initramfs. I usually never use initramfs - don't quite understand it

But my new system is using it, and booting fine.

NOW, I want to make kernel changes and install a modified kernel. After configging, I do

make
make modules_install
make install

The latter puts my new kernel in /boot - seems fine. Then, I do

grub-mkconfig -o /boot/grub/grub.cfg

This creates a new Grub config, however (this is the part that seems weird), it associates the OLD initramfs from the genkernel kernel with my new kernel. When I try to boot the new one, I get told that the root fs cannot be found. The root is specified as a UUID, and I check inside the grub.cfg, and can see that the UUID for the old kernel AND new kernel is the same. I google around, and find that you can replace these UUID with a good old /dev/sdaX. I try that. Still NO GO.

I wonder if the initramfs for the "wrong" kernel is screwing me up?

I'd like to get a simple step-by-step of how to install and run a modified kernel using Grub2. As you can see, I've got all the basics down. Is this supposed to be all there is to it? I am really determined to figure this out, rather than go back to Grub legacy. Gotta keep moving forward

Thanks for the help.

Roman_Gruber · Posted: Mon Sep 19, 2016 8:52 am Post subject:

I tell you my approach with grub2 since years.

Install once grub2 with a binary distro, like linux mint, arch linux, ubuntu livecd with the binary distro.

=>> Reuse that grub2 without ever updating hte binary distro. <<==

That implies that I only install grub once and keep it as is. Grub refers to any grub / grub2 / grub beta installation. Therefore I keep the installation medium on the shelf, its sysrescue cd 4.6.0 for this notebook, as any newer livecd do not work with this grub installation. it seems grub is not compatible with newer installations here.

With every new created kernel i do the following

set symlink by hand to /usr/src/linux
create .config
set proper local version with datecode
make --jobs 8 && make --jobs 8 modules install
cp bzimage to /boot with a proper name for the kernel
create a new boot entry by hand for grub with an editor like nano. Basically swap out title, swap out kernel in use. Reuse initramfs from genkernel.

I never ever update the initramfs from genkernel or my grub(1/beta/2) since years on different boxes.

The initramfs here are just instructions to do the luks / lvm magic.

=>> You need to tweak your kernel probably, determine whats needed to boot your box. <<=

Thats essential so you can slim down your kernel to the needed modules and prevent future issues with kernel updates.

Personal opinion: I do not recommend to use these scripts of mass destruction to manipulate the grub.cfg. You may be able to tweak it but I think its much faster and easier to understand whats beeing done when you do it by hand with a text editor.

As said, change the number of which boot title is loaded, change the title / kernel version of the boot section in your grub.cfg.

DONAHUE · Posted: Mon Sep 19, 2016 12:39 pm Post subject:

edit the grub.cfg for booting the new kernel to eliminate the initrd line.
if using a GPT disk suggest using PARTUUID vice UUID. PARTUUID available by running blkid.
_________________
Defund the FCC.

Roman_Gruber · Posted: Mon Sep 19, 2016 1:29 pm Post subject:

depends what your box need. you may still need an initramfs

Punchcutter · Guru Joined: 11 Feb 2007 Posts: 354

Thanks for the response. Roman_Gruber, esp thanks for the long, thoughtful notes... but unfortunately I need something more direct and practical to get me past this problem :lol:

I would like to do what you are doing, having deeper understanding of exactly how booting works, down to the metal, but I'm not quite there yet, and I really need to get this box back to working status quickly.

Another fun fact: The box was in fact booting just fine, running X, and doing what I wanted it to do right after the install. Then, for some reason that I cannot fathom, X.org stopped working because the video driver module i915 suddenly could not be loaded (IIRC, I was told "invalid argument"). I am mystified as to how that could have happened. Anyway, that's when I started building my new kernel and trying to boot it.

As a stopgap, if someone can offer a clue how I can get modprobe i915 to work, at least I'd be able to run the box on the original genkernel-created kernel. Of course I will still need to get back soon to building a new kernel, but at least the immediate pain would be relieved. Here's another bit of evidence related to that: at the same time i915 started not loading, I also noticed that when I boot, the console does not go into (what I think is) frame buffer mode (i.e. where the text turns tiny), but stays super-big.

DONAHUE, I tried removing the initrd line from my grub.cfg.....not by editing the file, but by doing a live-edit at boot time, by pressing "e". The result of that was a kernel panic and stack trace vomited all over my screen

My disk is not GPT, it's MBR. I tried GPT originally when I began to install on this box, and I couldn't get it to boot at all, so I redid the whole thing with MBR.

Finally... I have indeed referred to the docs and wiki, but have not, strangely, been able to find any clear, direct documentation of "how to build and install a new kernel on an existing Gentoo system using Grub2." Often docs are lacking for things that Just Work, but in my experience Grub2 can hardly be described this way

DONAHUE · Posted: Tue Sep 20, 2016 1:23 pm Post subject:

I specialize in step by step.
What boot media are you using? If not system rescue cd or usb suggest switch to it. sysresccd can be booted to an xfce4 GUI that provides midori browser as well as terminal window allowing copy and paste
what is the make and model of the computer or the motherboard and cpu if a homebrew?
Boot the install media and mount the gentoo partitions then run:

Punchcutter · Guru Joined: 11 Feb 2007 Posts: 354

Thanks DONAHUE... I will gratefully follow instructions a bit later and follow up. But quick question: Do I really need to boot from sysresccd? My box boots fine from genkernel kernel, it's just that Xorg doesn't work (bec module load fail), so I can't do anything too useful with it

But if running those commands from having booted off the HDD will be ok, I'll do that.

DONAHUE · Posted: Wed Sep 21, 2016 12:03 am Post subject:

Sorry I had concluded you were now 'bootless" . Booting the installed gentoo will be better than going into chroot. Sysresccd does a good job of sussing out drivers/modules and does have all tools and a browser. Also sorry to be late answering, I lawn mowered my comcast connection, spliced it, comcast gave away my dhcp license since I wasn't using it and a struggle ensued ...
_________________
Defund the FCC.

Punchcutter · Guru Joined: 11 Feb 2007 Posts: 354

Here are the pastes:

lspci -k
lshw | grep -i driver
lsmod
blkid
/proc/cpuinfo
Linux 4.1.15-gentoo-r1 .config
grub-mkconfig

Further help greatly appreciated. The machine is a Dell Vostro 260s.

[Moderator edit: changed bare unlabeled URLs to [url] tags labeled with their type. OP: please consider doing this as part of your post next time. -Hu]

DONAHUE · Posted: Wed Sep 21, 2016 4:45 pm Post subject:

noting that the kernel version is gentoo-sources-4.1.15-r1 which is perhaps 1-1/2 years old:
Is it likely that you updated xorg more recently than building the genkernel that used to run X but lost that ability?
The configuration of my gentoo-sources-4.7.3 has some significant changes in Graphics Support for intel from 4.1.15-r1.
When I worked with proprietary drivers, xorg -- kernel -- driver compatibility used to be a problem. Portage checked compatibility and issued more or less helpful warnings. Perhaps there is a similar problem now with open source intel?
Thought 1: run

Punchcutter · Guru Joined: 11 Feb 2007 Posts: 354

DONAHUE · Posted: Thu Sep 22, 2016 2:02 pm Post subject:

I f you would boot the genkernel that boots to the CLI and try to start X. then pastebin /var/log/Xorg0.log.
Does eselect kernel list show that you have linux-4.4.6-gentoo (The latest stable)) on board? Might be worthwhile to run genkernel all for 4.4.6, make a new grub.cfg, repeat the emerge of xorg and the drivers. then reboot to this new kernel. The new kernel will have a new /lib64/modules/4.4.6 to load from. In short:

DONAHUE · Posted: Sat Sep 24, 2016 5:29 pm Post subject:

I have emerged and run genkernel on gentoo-sources-4.1.15-r1 and gentoo-sources-4.4.6. Both booted. Only gentoo-sources-4.4.6 would run X, gentoo-sources-4.1.15-r1 failing to run X while complaining about DRI. The config files graphics support sections are different in how they handle i915. It appears the xorg-server/kernel developers did not maintain backward compatibility. Recommend you move on to an unmodified 'genkernel all' of gentoo-sources-4.4.6 for a bootable GUI capable system. grub2 should be able to handle a new version number without initrd ambiguity. Will work up a stripped down manual kernel .config for gentoo-sources-4.7.4 for you based on my own. The different version numbers should avoid grub2's initrd misbehavior.
_________________
Defund the FCC.

DONAHUE · Posted: Sat Sep 24, 2016 11:40 pm Post subject:

https://paste.pound-python.org/show/WmHrGum9nu7m6wZMndlg/ holds a kernel-4.7.4 config based on the one I am using currently. If you wish to try it, suggest:

axl · Veteran Joined: 11 Oct 2002 Posts: 1144 Location: Romania

u're right original poster.

u dont need initrd.

what you do need is a phone with a camera. that can take a picture of an actual error that someone could help with.

Punchcutter · Guru Joined: 11 Feb 2007 Posts: 354

DONAHUE, thanks so much for all the work you put into this. I must admit, I tried to cut the solution short by taking the knowledge you provided about incompatibility, and just upgraded my kernel to 4.4.6, did the usual stuff needed to run it, remerged my Xorg, and tried it. But the result was another kernel panic :cry:

So I broke down, bec I've pretty much had it with this, and just followed your instructions step by step to go to 4.7.4, using the config you provided, and voila, I get a booting system that runs Xorg as well. Sigh. There was nothing unexpected in your instructions, though.... nothing that would make me go "oooh, that's why it works." Pretty much the same stuff I did for 4.4.6.

Here's my grub.cfg, if you're still interested: http://bpaste.net/show/4816f90cde37

So, I'm still mystified. I looked into the grub.cfg a bit... not TOO hard, bec I'm tired, but could not see what might make the 4.7.4 kernel bootable, while the 4.4.6 or 4.1.15 goes down in flames.

Anyway... running. Thanks again.

DONAHUE · Posted: Mon Sep 26, 2016 1:44 pm Post subject:

I did not see an error in the stuff you pastebined; thus the hard way solution. I still believe the X failure was caused by a loss of backward compatibility between barely older kernel and newer xorg-server and xf86-video-intel. The panics did not get investigated; we have bypassed them. If you are still interested: boot 4.4.6 to a panic post a picture as axl suggested and we can look.
The 4.7.4 is based on pappy's kernel seed 3.3.9 (Loved his work, so saved a copy when he sold the shop) updated via make oldconfig, then modified to suit my machine, then modified to suit your machine.
_________________
Defund the FCC.