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redcap
n00b
Joined: 10 Jul 2010
Posts: 35
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 Posted: Sat Dec 23, 2017 11:40 am Post subject: [Solved] Kernel panics at boot on new system |
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Hi there,
I'm trying to setup a new Gentoo system on a Lenovo laptop. Everything went smoothly for the most part, however, the kernel I compiled
crashes early in the boot process. I bootstrapped the system using a systemrescue cd.
To configure my kernel, I took the kernel config from that cd, then
| Code: |
make localmodconfig
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and then some minor adjustments.
The resulting kernel cfg:
[url]
https://paste.pound-python.org/show/itUweUH8hIghQbbeMO2s/
[/url]
For reference, the original kernel config:
[url]
https://paste.pound-python.org/show/ELk1XI6u7JJFFtHRN9A1/
[/url]
And the kernel version of the bootstrapping system:
| Code: |
root@sysresccd /mnt/gentoo % uname -a
Linux sysresccd 4.9.52-std511-amd64 #2 SMP Wed Sep 27 19:47:36 UTC 2017 x86_64 Intel(R) Core(TM) i5-7200U CPU @ 2.50GHz GenuineIntel GNU/Linux
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Here is a picture of the actual kernel output when panicing:
[url]
https://imagebin.ca/v/3lfoUZpQT53r
[/url]
When setting up the system I roughly followed the handbook but made some adjustments.
The most relevant being that I went for a lvm over luks setup with all partition apart from /boot
being encrypted. I put together a small initframfs that I packaged into the kernel at compile time.
This is my init script in the initramfs:
| Code: |
#!/bin/busybox sh
rescue_shell() {
echo "Something went wrong. Dropping to a shell."
exec sh
}
# Mount the /proc, /sys and /dev filesystems.
mount -t proc none /proc
mount -t sysfs none /sys
mount -t devtmpfs none /dev
# Do your stuff here.
echo "Waiting for /dev"
sleep 3
echo "Unlocking ..."
cryptsetup -T 5 --allow-discards luksOpen /dev/sda5 gentoocrypt
echo "Activating logical volumes"
lvm vgscan --mknodes
lvm lvchange -aly vg1/root
echo "Mounting root..."
# Mount the root filesystem.
mount -o ro /dev/mapper/vg1-root /mnt/root || rescue_shell
mount -o ro /dev/mapper/vg1-var /mnt/var || rescue_shell
# Clean up.
umount /proc
umount /sys
umount /dev
# Boot the real thing.
exec switch_root /mnt/root /sbin/init
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Anyone got any ideas what might cause the kernel panic. Any help is greatly appreciated.
Thanks in advance and happy holidays 
Last edited by redcap on Mon Dec 25, 2017 1:10 am; edited 1 time in total |
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NeddySeagoon
Administrator
Joined: 05 Jul 2003
Posts: 43419
Location: 56N 3W
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| Posted: Sat Dec 23, 2017 2:23 pm Post subject: |
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redcap,
Your kernel loaded and everything got started, so grub is leading the kernel.
Then it wanted to kill init, which is a very bad thing.
I don't see any | Code: | | echo "Unlocking ..." |
in your photo,
Nor the other echos in the initrd.
Is your initrd actually being called?
Its worth adding to the commands where its missing, then when they fail, you can use the rescue shell to poke about.
If the kernel slill panics, your initrd is not being used.
_________________
Regards,
NeddySeagoon
Computer users fall into two groups:-
those that do backups
those that have never had a hard drive fail. |
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Hu
Moderator
Joined: 06 Mar 2007
Posts: 13990
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| Posted: Sat Dec 23, 2017 5:30 pm Post subject: |
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| You appear to have done at least some of the setup for the initramfs. From what you posted, we can't verify if you did all of it. Is /usr/src/initramfs a directory or is it a kernel initramfs manifest? If it is a directory, what is the output of find /usr/src/initramfs/ -ls? If it is a file, what is the output of cat -n /usr/src/initramfs? |
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redcap
n00b
Joined: 10 Jul 2010
Posts: 35
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| Posted: Sat Dec 23, 2017 10:52 pm Post subject: |
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Hi there,
I've modified the init file in the following way:
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(chroot) sysresccd / # cat /usr/src/initramfs/init
#!/bin/busybox sh
echo "Starting init in initramfs..."
rescue_shell() {
echo "Something went wrong. Dropping to a shell."
exec sh
}
# Mount the /proc, /sys and /dev filesystems.
mount -t proc none /proc || rescue_shell
mount -t sysfs none /sys || rescue_shell
mount -t devtmpfs none /dev || rescue_shell
# Do your stuff here.
echo "Waiting for /dev"
sleep 3
echo "Unlocking ..."
cryptsetup -T 5 --allow-discards luksOpen /dev/sda5 gentoocrypt
echo "Activating logical volumes"
lvm vgscan --mknodes
lvm lvchange -aly vg1/root
echo "Mounting root..."
# Mount the root filesystem.
mount -o ro /dev/mapper/vg1-root /mnt/root || rescue_shell
mount -o ro /dev/mapper/vg1-var /mnt/var || rescue_shell
# Clean up.
umount /proc
umount /sys
umount /dev
# Boot the real thing.
exec switch_root /mnt/root /sbin/init
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The first echo in the file produces no output while booting. It seems that the init file is never executed.
/usr/src/initramfs is a directory. The requested output is
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(chroot) sysresccd / # find /usr/src/initramfs/ -ls
274205 4 drwxr-xr-x 12 root root 4096 Dec 22 17:37 /usr/src/initramfs/
274207 4 drwxr-xr-x 2 root root 4096 Dec 22 16:56 /usr/src/initramfs/bin
274218 1992 -rwxr-xr-x 1 root root 2037672 Dec 22 16:55 /usr/src/initramfs/bin/busybox
274215 4 drwxr-xr-x 2 root root 4096 Dec 22 16:39 /usr/src/initramfs/root
274214 4 drwxr-xr-x 2 root root 4096 Dec 22 16:39 /usr/src/initramfs/proc
274210 4 drwxr-xr-x 2 root root 4096 Dec 22 16:39 /usr/src/initramfs/lib
274216 4 drwxr-xr-x 2 root root 4096 Dec 22 17:32 /usr/src/initramfs/sbin
276685 2716 -r-xr-xr-x 1 root root 2777648 Dec 22 17:10 /usr/src/initramfs/sbin/lvm
276687 2528 -rwxr-xr-x 1 root root 2585224 Dec 22 17:32 /usr/src/initramfs/sbin/cryptsetup
274212 4 drwxr-xr-x 3 root root 4096 Dec 22 16:39 /usr/src/initramfs/mnt
274213 4 drwxr-xr-x 3 root root 4096 Dec 22 18:08 /usr/src/initramfs/mnt/root
404137 4 drwxr-xr-x 2 root root 4096 Dec 22 18:08 /usr/src/initramfs/mnt/root/var
274209 4 drwxr-xr-x 2 root root 4096 Dec 22 16:39 /usr/src/initramfs/etc
274208 4 drwxr-xr-x 2 root root 4096 Dec 22 18:09 /usr/src/initramfs/dev
276690 0 crw-rw-rw- 1 root root 1, 8 Dec 21 19:11 /usr/src/initramfs/dev/random
276689 0 crw-rw-rw- 1 root root 1, 9 Dec 21 19:11 /usr/src/initramfs/dev/urandom
274211 4 drwxr-xr-x 2 root root 4096 Dec 22 16:39 /usr/src/initramfs/lib64
274217 4 drwxr-xr-x 2 root root 4096 Dec 22 16:39 /usr/src/initramfs/sys
276688 4 -rwxr-xr-x 1 root root 821 Dec 23 21:49 /usr/src/initramfs/init
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I also took a look at the entry created in /boot/grub/grub.cfg corresponding to the kernel. It reads as follows:
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### BEGIN /etc/grub.d/10_linux ###
menuentry 'Gentoo GNU/Linux' --class gentoo --class gnu-linux --class gnu --class os $menuentry_id_option 'gnulinux-simple-a17a5e94-fcb4-492e-b3a2-a79d0696ff81' {
load_video
if [ "x$grub_platform" = xefi ]; then
set gfxpayload=keep
fi
insmod gzio
insmod part_gpt
insmod ext2
set root='hd0,gpt6'
if [ x$feature_platform_search_hint = xy ]; then
search --no-floppy --fs-uuid --set=root --hint-bios=hd0,gpt6 --hint-efi=hd0,gpt6 --hint-baremetal=ahci0,gpt6 19a90a46-5fc7-439d-bf0d-3fe5e8825146
else
search --no-floppy --fs-uuid --set=root 19a90a46-5fc7-439d-bf0d-3fe5e8825146
fi
echo 'Loading Linux 4.14.8-gentoo-r1 ...'
linux /vmlinuz-4.14.8-gentoo-r1 root=/dev/mapper/vg1-root ro
}
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I'm not quite sure if the kernel parameter root=/dev/mapper/vg1-root ro is correct, since that device is encrypted. However, when I removed that parameter in GRUB edit mode, the issue was still present. |
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NeddySeagoon
Administrator
Joined: 05 Jul 2003
Posts: 43419
Location: 56N 3W
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| Posted: Sat Dec 23, 2017 11:57 pm Post subject: |
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redcap,
| grub.cfg: | echo 'Loading Linux 4.14.8-gentoo-r1 ...'
linux /vmlinuz-4.14.8-gentoo-r1 root=/dev/mapper/vg1-root ro |
There would normally be another two lines there for the initrd.
How do you make and load the initrd?
_________________
Regards,
NeddySeagoon
Computer users fall into two groups:-
those that do backups
those that have never had a hard drive fail. |
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redcap
n00b
Joined: 10 Jul 2010
Posts: 35
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NeddySeagoon
Administrator
Joined: 05 Jul 2003
Posts: 43419
Location: 56N 3W
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| Posted: Sun Dec 24, 2017 12:37 am Post subject: |
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redcap,
That's correct. The embedded initrd works. Its the only way with a EFI stub kernel if you need an initrd.
While you have a boot loader, its easier to debug and fix if the intrd is separate.
I'm surprised that you need | Code: | 276690 0 crw-rw-rw- 1 root root 1, 8 Dec 21 19:11 /usr/src/initramfs/dev/random
276689 0 crw-rw-rw- 1 root root 1, 9 Dec 21 19:11 /usr/src/initramfs/dev/urandom |
since DEVTMPFS should provide them.
You will also need /dev/{null,console,tty} and your HDD nodes if you need to provide a working static /dev to your initrd.
There may bo other things too like setting the $PATH, so commands look in /sbin or /bin or using the full path in the initrd init script.
_________________
Regards,
NeddySeagoon
Computer users fall into two groups:-
those that do backups
those that have never had a hard drive fail. |
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redcap
n00b
Joined: 10 Jul 2010
Posts: 35
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| Posted: Sun Dec 24, 2017 1:15 am Post subject: |
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I must admit that is just copied
/dev/random and /dev/random
to the initrd because it was suggested in the custom initramfs guide
https://wiki.gentoo.org/wiki/Custom_Initramfs#DM-Crypt
I did not realize if or why it was necessary. So if I understood you correctly,
/usr/src/initramfs/dev
can be left empty as long as I have CONFIG_DEVTMPFS=y in the kernel and a long
enough sleep period in the init script to allow the kernel to populate /dev?
I will try to separate the initrd from the kernel to facilitate debugging.
Just to make sure that I got everything right: Your advice concerning $PATH pertains to the lvm and cryptsetup binaries but
the echo statements should be executed successfully either way as soon as the execution of the script started succesfully
since echo is a shell built-in?
Anyways, thanks for your help and I apologize for being a little dense. Getting the first running kernel on a new system has always been
the hardest part of a Gentoo install for me. |
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redcap
n00b
Joined: 10 Jul 2010
Posts: 35
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| Posted: Mon Dec 25, 2017 1:10 am Post subject: |
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NeddySeagoon,
thanks very much for your input. I managed to boot my system successfully.
The reason for the kernel panic where indeed missing /dev/{null,console,tty}
nodes. I simply overlooked those in the initramfs guide. So it was entirely my
own stupidity that lead to me wasting a few hours of my life. Well, at least that
error won't happen to me again.
Anyways, thanks again and enjoy the holidays |
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