Access to shell during or after kernel panic?

Polytropon freebsd at
Fri Nov 11 08:18:42 UTC 2016

On Fri, 11 Nov 2016 00:18:39 -0700, Mick mtn wrote:
> FreeBSD 11R on macbook pro.
> does not see dvd, yet the system was installed via
> FreeBSD-11.0-RELEASE-amd64-dvd1.iso
> ----------------------------------------------------------------
> partial panic printout:
> module visa failed to register: 17
> kbd0 at kbdmux0
> Panic Module_register_init
> ...
> ...
> ...
> #1 0 . . . kdb backtrace           at 0x67
> #2 ...      vpanic                       at 0x182
> #3          panic                         at 0x43
> #4          module_register_init at 0x11c
> #5          mi_startup                 at 0x118
> #6          btext                          at 0x2c
> uptime 1s
> -----------------------------------------------------------------
> I can see the files in the rescue directory, but can not move to that
> directory or issue commands like rescue/vi -v boot/loader.conf

After a kernel panic, you usually cannot access the shell anymore,
not locally, not remotely. But you can press Ctrl+Alt+Esc to enter
the kernel debugger (which probably won't be much help at this

> ANY HINTS on possible keyboard combinations to force boot from dvd?
> Holding "C" on boot is not getting the result i expected.

Is pressing C at boot a Mac-specific action?

When you can access the FreeBSD loader prompt, entering the
command "boot -C" will usually try to boot from optical media.
This is the same prompt where you can unload unwanted kernel
modules, set a different kernel, or enter "boot -s" to continue
into single user mode (where mounting / r/w and editing files
using /rescue/vi would be possible).

Magdeburg, Germany
Happy FreeBSD user since 4.0
Andra moi ennepe, Mousa, ...

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