[gentoo-user] Re: kernel panic -- finding proper config diff

[walt <w41ter@gmail.com>]

On 10/21/2009 11:25 AM, Maxim Wexler wrote:
> Hi group,
> 
> Did linux#make menuconfig followed by linux# make && make
> modules_install on the .2.6.30-gentoo-r7 sources. And copied over the
> new kernel and rebooted.
> 
> The kernel panicked. The relevant messages are:
> 
> <...>
> VFS: Mounted root (ext2 filesystem) readonly on device 8:1,
> Freeing unused kernel memory: 276k freed
> Warning: unable to open an initial console

That warning is interesting.  This is from the kernel sources:
 if (sys_open((const char __user *) "/dev/console", O_RDWR, 0) < 0)
     printk(KERN_WARNING "Warning: unable to open an initial console.\n");

In the dark ages, before udev, /dev/console had to be created in the bare
/dev directory (i.e. before anything is mounted on /dev) to prevent this
sort of error.  I thought it had been solved, but maybe I'm wrong about
that.

Of course, I'm not sure I don't get the same warning, but if I do it
flashes by so quickly I can't read it.

The message clearly states that / is mounted readonly, but that test for
/dev/console is asking for read/write. Maybe that's why the test fails,
dunno.  And I don't know if that warning is important.

Nowadays udev uses a tmpfs in RAM to populate /dev with devices, but
at the point your kernel panics, that tmpfs doesn't exist yet, so you
are stuck with the /dev directory on / including its readonly status,
I'm assuming.

Anyone else know?