[SOLVED] 14.1 usb boot stick kernel panic

tuubaaku · 06-01-2016, 06:21 PM

I'm on 14.1, 32-bit, with a generic smp kernel and initrd. I'm using lvm and ext4. I tried creating a usb boot stick with the Slackware setup script, but when I try booting it I get the following error:
kernel panic - not syncing: VFS: unable to mount root fs on unknown block (0,0)

I'm thinking that maybe the USB stick needs an initrd, but the script doesn't create one? Does that sound right? If that's the issue, is there a good way to create a boot stick that won't cause the kernel panic? Any thoughts?

Thanks.

Emerson · 06-01-2016, 07:45 PM

Kernel wants to mount / before USB is initialized, add rootwait to your kernel command line.

tuubaaku · 06-01-2016, 08:15 PM

Thanks, Emerson.

I tried booting with a special kernel command with the rootwait option, and the boot messages did show that it was waiting for root. Unfortunately, after waiting a few minutes, nothing happened, so that doesn't seem to be the issue.

Any other thoughts?

ReaperX7 · 06-01-2016, 09:50 PM

You're using a generic kernel. Try a huge kernel. You probably have a driver issue.

Didier Spaier · 06-02-2016, 04:41 AM

The script that creates the boot stick is /var/log/setup/setup80-make-bootdisk.

It copies vmlinuz to the USB stick, but no initrd.

Rationale as I understand it:

This script's main purpose is to make an "emergency" boot stick, allowing you to start Slackware in case where the boot loader can't do that for some reason after installation. When you run it during the "CONFIGURE" step after a fresh installation, vmlinuz is a symlink to a huge kernel, so there is no need for an initrd.

If you want to run this script after installation (for instance from "pkgtool") you could:

either tentatively make of /boot/vmlinuz a symlink to a huge kernel,
or modify the script to make it copy your initrd to the boot stick and adapt the config files of the boot loaders accordingly.

The first way is simpler and faster, the second could be a learning exercise

tuubaaku · 06-02-2016, 07:37 PM

OK, I tried making a boot disk with the huge kernel, but I still got the same error.

The second option of copying the initrd over and updating the config - is that the only way to make this work? Has anyone else had trouble with an LVM/ext4 boot disk, or does this work for everyone else?

ReaperX7 · 06-03-2016, 12:46 AM

Check your fstab. It might need to be set to mount by UUID rather than a device name node.

Didier Spaier · 06-03-2016, 02:45 AM

Quote:

Originally Posted by tuubaaku

OK, I tried making a boot disk with the huge kernel, but I still got the same error.

The second option of copying the initrd over and updating the config - is that the only way to make this work? Has anyone else had trouble with an LVM/ext4 boot disk, or does this work for everyone else?

We miss precise information to help you. Please indicate at least the content of /etc/fstab and of /etc/lilo.conf and the output of "df -h".

Emerson · 06-03-2016, 03:03 AM

Code:

kernel panic - not syncing: VFS: unable to mount root fs on unknown block (0,0)

This is clear message kernel has no drivers to access root device, what's in fstab is irrelevant at this stage of boot. You need all modules loaded which are needed to mount USB and access the root filesystem and you probably still need the rootwait option.

Didier Spaier · 06-03-2016, 04:48 AM

Quote:

Originally Posted by Emerson

Code:

kernel panic - not syncing: VFS: unable to mount root fs on unknown block (0,0)

This is clear message kernel has no drivers to access root device, what's in fstab is irrelevant at this stage of boot. You need all modules loaded which are needed to mount USB and access the root filesystem and you probably still need the rootwait option.

At this time we do not know what the problem is. So please do not provide "solutions" not knowing what the problem is (the kernel panic is a symptom, no more) and do not discourage the OP to provide information that could be useful. The content of /etc/fstab is relevant.

@tubaaku: knowing how LVM is set is needed as well.

ReaperX7 · 06-03-2016, 05:01 AM

Kernel panic for vfs means that the root file system driver doesn't exist at boot, which is why I directed you to use the Huge kernel. The vmlinuz copied should be the vmlinuz-huge version. Checksum the huge kernel with the copied file and make sure its equal. If needed, try using the initrd with busybox and mdev to preload a few tools and extra modules if needed.

Emerson · 06-03-2016, 05:23 AM

Quote:

Originally Posted by Didier Spaier

At this time we do not know what the problem is. So please do not provide "solutions" not knowing what the problem is (the kernel panic is a symptom, no more) and do not discourage the OP to provide information that could be useful. The content of /etc/fstab is relevant.

@tubaaku: knowing how LVM is set is needed as well.

Please do not talk unless you know what you are talking about.

Code:

unable to mount root fs on unknown block (0,0)

This (0,0) indicates the device is not accessible. Or, in case of UEFI boot root= parameter is not passed to the kernel. In case the partition table is not recognized or root filesystem is not supported by given kernel the numbers are not zero any more.

tuubaaku · 06-03-2016, 07:08 AM

Thanks for the replies. I will post back later with more information and/or results.

aaazen · 06-04-2016, 03:18 PM

Quote:

Originally Posted by Didier Spaier

The script that creates the boot stick is /var/log/setup/setup80-make-bootdisk.

It copies vmlinuz to the USB stick, but no initrd.

Maybe the script should copy vmlinuz-huge instead of vmlinuz?

Didier Spaier · 06-04-2016, 04:05 PM

mlin

Quote:

Originally Posted by comet.berkeley

Maybe the script should copy vmlinuz-huge instead of vmlinuz?

I don't think so:

This script is supposed to be used just after installation, and at this point vmlinuz is a symlink to the huge kernel anyway.
If it is used later, the user can just tentatively modify the symlink if need be.

This being said I am not the decider.

Quote:

While we are at it, I found another bug in setup80-make-bootdisk in Slackware64-current.

When running from an install DVD (running busybox) then the syslinux command fails at line 208:

Code:

   syslinux -s /dev/$STICK 1> /dev/null 2> /dev/null

The syslinux command requires run time libraries which are not available.

Code:

#ldd /usr/bin/syslinux
        linux-vdso.so.1 (0x00007fff5819f000)
        libc.so.6 => /lib64/libc.so.6 (0x00007f058053f000)
        /lib64/ld-linux-x86-64.so.2 (0x000055a1475a2000)

To run syslinux the script needs to do something like this:

1) mount --bind /dev /mnt/dev
2) chroot /mnt
3) syslinx ..[/q
o
wish list: If only syslinux had a -r option like lilo.

Not sure about that. I am puzzled because I get another output of ldd on slackware-current:

Code:

bash-4.3$ ldd syslinux
        linux-gate.so.1 (0xb77e7000)
        libc.so.6 => /lib/libc.so.6 (0xb7615000)
        /lib/ld-linux.so.2 (0x800bf000)

It's not the same arch but I doubt that fundamentally changes something. Anyway I will makee some tests tomorrow