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Kernel panic after install - SOLVED
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Progman3K
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PostPosted: Tue Mar 18, 2014 7:29 pm    Post subject: Kernel panic after install - SOLVED Reply with quote

Hi,

Just finished installing on a laptop and when I restart, Grub2 come up, allows me to select the kernel I compiled.

Then it loads the kernel, which begins initialization but regrettably ends with a kernel-panic

Is there a way to recover the messages that led up to the panic?
If the font was just a bit smaller, I think I could make out what the problem really is.

What's the best way to figure out what is going on?


Last edited by Progman3K on Tue Mar 18, 2014 11:05 pm; edited 1 time in total
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ferreirafm
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Joined: 28 Jul 2005
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Location: Sao Paulo, Brazil

PostPosted: Tue Mar 18, 2014 7:51 pm    Post subject: Reply with quote

Progman3K,
If you has got a kernel panic, it means you couldn't be able to load your kernel and else, you haven't any control of your box at all.
No remedy on this which I'm aware. Try to recompile your kernel.
Best.
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NeddySeagoon
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Joined: 05 Jul 2003
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PostPosted: Tue Mar 18, 2014 8:03 pm    Post subject: Reply with quote

Progman3K,

Try a video of the boot process. You may get a few useful images.
There are other alternatives too.

Favourite would be a serial console. That means the system that fails to boot needs a real serial port, or you won't get the early messages.

Harder is some analysis by yourself or others, of the boot process. We need your grub.cfg, lspci output and tho kernel .config file
How you change the font size varies with your console driver and it may not be come into effect until after the panic anyway.

Messages like "tried to kill init!" "unknown-block(x,y)" where x and y are numbers would be useful.

How did you make your kernel?
Are you using (U)EFI booting or not ?
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NeddySeagoon

Computer users fall into two groups:-
those that do backups
those that have never had a hard drive fail.
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Progman3K
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PostPosted: Tue Mar 18, 2014 11:05 pm    Post subject: Reply with quote

Thank you for the replies!

Got it to boot!

Even though I followed the handbook instructions with Grub2, it appears something was preventing the boot-by-disk-UUID.
I manually changed the line in /boot/grub/grub.cfg from

root=UUID=somehexstring
to
root=/dev/sda3

and now it boots.

The odd thing is that I checked with GParted while running the rescuecd and the UUID GParted displayed did match the the sda3 UUIDl

It is a non-UEFI system.
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NeddySeagoon
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PostPosted: Wed Mar 19, 2014 7:23 pm    Post subject: Reply with quote

Progman3K,

Ahh. So many objects have UUIDs

The partition has a UUID, the filesystem on the partition has a (different) UUID
root=UUID=somehexstring needs to be the UUID of the filesystem on sda3, not the UUID of the partition.
e.g.
Code:
$ /sbin/blkid
/dev/sda1: UUID="9392926d-6408-6e7a-8663-82834138a597" TYPE="linux_raid_member" PARTUUID="0553caf4-01"

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NeddySeagoon

Computer users fall into two groups:-
those that do backups
those that have never had a hard drive fail.
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Progman3K
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PostPosted: Sat Mar 22, 2014 1:16 am    Post subject: Reply with quote

I believe there is something else going on, Neddy

Code:
mount /boot
grub2-mkconfig -o /boot/grub/grub.cfg

generates three menu entries in /boot/grub/grub.cfg with these launch-lines:
Quote:

linux /vmlinuz-3.12.13-gentoo root=UUID=36041925-fd70-4406-abd8-b6dd28b22422 ro init=/usr/lib/systemd/systemd
linux /vmlinuz-3.12.13-gentoo root=UUID=36041925-fd70-4406-abd8-b6dd28b22422 ro init=/usr/lib/systemd/systemd
linux /vmlinuz-3.12.13-gentoo root=UUID=36041925-fd70-4406-abd8-b6dd28b22422 ro single init=/usr/lib/systemd/systemd


As you can see, the hex ID does correspond to the proper partition, /dev/sda3

Code:
/sbin/blkid
Quote:

/dev/sda1: UUID="9e5d94a5-9d10-46f3-aba1-a9a090afa0a9" TYPE="ext2"
/dev/sda2: UUID="e87bf72a-fc52-4646-acc6-31cfad99849c" TYPE="swap"
/dev/sda3: UUID="36041925-fd70-4406-abd8-b6dd28b22422" TYPE="ext4"


However, if I leave things like that, rebooting causes a kernel panic.
I can see a function called mount_block_root in the call-stack, so it appears to be failing to mount /

If I edit the launch-lines in /boot/grub/grub.cfg to read like this:
Quote:

linux /vmlinuz-3.12.13-gentoo root=/dev/sda3 ro init=/usr/lib/systemd/systemd
linux /vmlinuz-3.12.13-gentoo root=/dev/sda3 ro init=/usr/lib/systemd/systemd
linux /vmlinuz-3.12.13-gentoo root=/dev/sda3 ro single init=/usr/lib/systemd/systemd


Then the system boots.

I don't understand it either.
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