kern/153996: [zfs] zfs root mount error while kernel is not located in /boot/kernel

[Garrett Cooper]

The following reply was made to PR kern/153996; it has been noted by GNATS.

From: Garrett Cooper <gcooper at FreeBSD.org>
To: Alexander Naumochkin <alexander.naumochkin at gmail.com>
Cc: bug-followup <bug-followup at freebsd.org>
Subject: Re: kern/153996: [zfs] zfs root mount error while kernel is not
 located in /boot/kernel
Date: Wed, 19 Jan 2011 09:54:45 -0800

 On Wed, Jan 19, 2011 at 9:17 AM, Alexander Naumochkin
 <alexander.naumochkin at gmail.com> wrote:
 > Wow! It starts! I've just typed boot GENERIC, and it starts and works!
 > Thank you very much Garrett!
 >
 > This will continue forever in next releases? I think it should be
 > documented in Handbook. How can I participate? If I can ever :)
 >
 > On Wed, Jan 19, 2011 at 12:20 PM, Garrett Cooper <gcooper at freebsd.org> wr=
 ote:
 >>
 >> On Tue, Jan 18, 2011 at 8:37 AM, Alexander Naumochkin
 >> <alexander.naumochkin at gmail.com> wrote:
 >> > Garrett,
 >> > now I have two kernels on my box:
 >> > 1. /boot/kernel/kernel =97 my working customized kernel
 >> > 2. /boot/GENERIC/kernel =97 GENERIC kernel
 >> > I tried the following expreriment:
 >> > # shutdown -r now
 >> > wait for loader menu and choose 6 - Escape to loader prompt
 >> > OK unload kernel
 >> > OK set kernelname=3D/boot/GENERIC/kernel
 >> > OK set module_path=3D/boot/GENERIC
 >> > OK load opensolaris
 >> > OK load zfs
 >> > OK boot
 >> > and got the same result: "MOUNT ROOT ERROR" while "Trying to mount roo=
 t from
 >> > zfs:zroot"
 >> > BTW, even if your method would work, it could not help in case of inst=
 all
 >> > misconfigured unbootable kernel. Let's say I install misconfigured ker=
 nel:
 >> > # make installkernel KERNCONF=3DBADKRNL
 >> > After this I get:
 >> > 1. bad kernel in /boot/kernel/kernel
 >> > 2. previous working kernel in /boot/kernel.old/kernel
 >> > 3. GENERIC kernel in /boot/GENERIC/kernel
 >> > I reboot and faced with unbootable system (because of BADKRNL as defau=
 lt).
 >> > In fact we have now completely unbootable system due the bug I've repo=
 rted
 >> > with this PR. Also this bug means that from now on we have no possibil=
 ity to
 >> > test custom kernels by installing it to alternate directory (with KODI=
 R
 >> > variable) =97 it will not boot anyway.
 >>
 >> Try set kernelname=3DGENERIC , etc. Or... just load the kernel modules
 >> and do: boot GENERIC, etc on the loader command line.
 
      It's been this way for ages with loader(8), so I doubt it's going
 to change too dramatically anytime soon :). That being said, the
 handbook [1] might need to be updated a bit with a working process (or
 unload needs to be properly fixed to unload everything if it's broken
 -- not sure). I'll have to see what happens when I issue those
 commands sometime on the command line.
      Regardless though -- if the process doesn't work as-is you should
 submit a doc update for the handbook so that a working process is
 available for end-users :).
 Cheers!
 -Garrett
 
 1. http://www.freebsd.org/doc/handbook/boot-blocks.html