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Kernel panic on Dell Vostro (first time using grub2 and gpt)
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Punchcutter
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PostPosted: Sun Jun 12, 2016 6:01 am    Post subject: Kernel panic on Dell Vostro (first time using grub2 and gpt) Reply with quote

Hi..... this is an install headache that I've had for about 6 months. Tried to install in January, failed, came back to it in April, failed, now I'm trying again. Very frustrating.

I'm installing on a Dell Vostro 260s small form-factor tower-type PC. It's an i3 dual core. The problem is this: when I try to boot, I'm getting some kind of kernel panic, with a dump of memory or something.

Long story short, I've followed the AMD64 install Handbook on the web carefully. I've installed Gentoo many times before and so I'm familiar with most of the nitty-gritties.

The main thing that's different this time is that I'm using Grub 2. I've only ever used Grub legacy (0.97) before. Seems the details of how to install kernels is different, but I think I'm doing it right. You run "make install" from your kernel dir, and then run "grub2-mkconfig -o /boot/grub/grub.cfg", right?

Oh, another thing that's different is that I've chosen a GPT disk label rather than MBR, and partitioned with parted for the first time rather than cfdisk. Again, figuring I need to get with the future :) I guess there are more variables in this thing than I remembered :oops: I found a note in the handbook about buggy BIOSes having trouble with GPT labels and how you might fix that (use fdisk -t dos to set the bootable flag), but that didn't fix the problem.

Here's a thing that I think may be the most relevant: I've now got this extra partition, only 2M, that parted reports has a flag of "bios_grub" set on it. And then there's my normal boot partition, initialized with ext2, that has flags "boot, esp" set. Forgive me... I really just don't know the significance of any of this.

Anyway, I've checked that my filesystem drivers and other basic h/w stuff is compiled into the kernel rather than using modules - that should be ok, I think.

Not sure exactly what info I should provide in order to get help here.

I thought this was a good chance to finally get with the times and start using GPT and Grub 2, finally, but maybe I just need to give up for the time being and go back to the old ways :(

Thanks very much for any help you can provide.
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C5ace
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Joined: 23 Dec 2013
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Location: Brisbane, Australia

PostPosted: Sun Jun 12, 2016 7:21 am    Post subject: Reply with quote

I installed Gentoo on 5 Laptops, several Desktops and Virtualmashines with Xfce4. Tried systemd, GPT, UEFI, EFI, Grub2. Never a sucessful smooth install. Lots of wasted time. Grub2 is still "Beta". Open-rc, MS-DOS, grub-static, EXT4 with disk labels work without any hitches if the boot disk is less than 2TB with 500M "Boot", 30G "Root", reminder "Home" and some with a "VirtualBox" partition if the user wants to run Windoze. I use my "Copy & Paste" installation script and genkernel to limit time on the keyboard. It just works!
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champ
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Joined: 25 Oct 2006
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PostPosted: Sun Jun 12, 2016 10:42 am    Post subject: Reply with quote

Punchcutter,

Two thoughts on grub2:

1. Did you run grub2-install before running grub2-mkconfig?

2. After running grub2-mkconfig check the file grub.cfg, that may help narrow down your problem.
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axl
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PostPosted: Sun Jun 12, 2016 10:57 am    Post subject: Reply with quote

I think the first thing you need to figure out is if you actually need gpt. I looked over the mobo from that system. seems some vendors add uefi to that chipset. not sure if that dell version has uefi. if it doesn't and u're actually using the default 500Gb drives, then perhaps u're better off using mbr.

If you DO have different main drive, and it's larger then 2tb, or if you do have uefi and try to boot in uefi mode, then severals things to check at first.

so why use gpt? uefi or large drives?
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axl
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PostPosted: Sun Jun 12, 2016 11:06 am    Post subject: Reply with quote

the thing is, gpt was created for efi systems. efi being a different kind of bios.

while normal bios looks for a mbr drive, efi systems look for a gpt drive. (at least at first).

so keeping this in mind, when trying to install grub, you both have to be booted in efi mode, and have the necessary version of grub installed.

grep GRUB /etc/make.conf
GRUB_PLATFORMS="coreboot efi-32 efi-64 emu multiboot pc qemu"

but if you have a normal bios without efi, there's really no point in using gpt if your machine has it's default 500Gb drive.
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NeddySeagoon
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Joined: 05 Jul 2003
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PostPosted: Sun Jun 12, 2016 12:29 pm    Post subject: Reply with quote

Punchcutter,

Once upon a time, there was no partition table at all. MSDOS could only use HDD up to 32 Mb. (Yep Megabytes)
The MSDOS partition table was introduced as a dirty hack to fix that. It only has four entries as it had to fit into the empty space at the end of C/H/S address 0,0,0, which is all the BIOS could ever read.
Along with the partition table came a standard that the first partition should always start at C/H/S 0,1,0 or head one in the outer cylinder. In those days HDD geometry mattered and there were lots of different geometries.

Fast forward a few years and HDD geometry was mapped out inside the drive, so it no longer had any physical meaning. HDD always appeared to have 63 sectors per track. That combined with the first partition always starting at C/H/S 0,1,0 meant that there was some unallocated space between the MBR and the start of the first partition. Lots of things have used this space over the years, including boot loaders like grub.

GPT does things slightly differently. The MBR is not used, so that GPT is backwards compatible with BIOS. BIOS closes its eyes and loads then executes the code in the MBR. GPT also creates a fake MSDOS partition table, that can carry the bootable flag to keep a BIOS happy. BIOS will not see a GPT table at all.
Another difference is that the GPT partition table starts in sector 1, so there is no longer any unallocated space before the first partition. It follows at the end of the primary copy of the GPT partition table. This means that to allocate space for your boot loader, you must make a small partition. That's your 2Mb bios_grub partition.
Grub uses it for itself. It does not contain a filesystem, you never mount it.

A few brain dead BIOS systems (Dell) not only check the bootable flag on the fake MSDOS partition table, they also check that the partition type is one that they expect to boot from. If the partition type is ee, they refuse to boot. Such a BIOS system will not boot from a HDD with a GPT partition table.
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those that do backups
those that have never had a hard drive fail.
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