Booting MFS from Secondary Partition

Jonathan McKeown j.mckeown at
Mon Mar 8 07:31:36 UTC 2010

On Saturday 06 March 2010 15:02:20 Martin McCormick wrote:
> Fbsd1 writes:
> > just dd the image to what ever drive you want
> 	That is the goal. The challenge is to launch a script
> that detects when the boot device has been unmounted as dd will
> not work on an active file system.


it may or may not work, but there's a sysctl for the geom subsystem which 
might do what you want.

sysctl kern.geom.debugflags=16

This used to be used (for all i know still can be) to allow writing metadata 
for (eg) building a gmirror on a mounted disk - it's often referred to as the 
``allow-footshooting'' flag.

That might allow you to dd your image onto the mounted disk - i'd either try 
it with a handy spare system or wait for someone more expert than i to 
comment, though.


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