kernel backup on 7.0

[Ivan Voras]

Jeremy Chadwick wrote:
> On Thu, Mar 06, 2008 at 01:58:08PM +0100, Ivan Voras wrote:
>> James López (BLuEGoD) wrote:
>>
>>> Not exactly.. What I mean is that I want to reinstall FreeBSD due to
>>> some accidentally deleted files and a behavior on sendfile :S
>>> So I would like to know if I can backup /boot and the overwrite it once
>>> I have freebsd installed again...
>> Yes. If you don't change FreeBSD versions or hardware, this will work.
> 
> Clarification: it _might_ work.
> 
> You need to keep in mind that the kernel/modules he's backing up will
> very likely *not* match all the binaries he has on his disks, library
> calls, possibly system calls, etc. etc...  This is why building world
> includes both all the binaries *as well* as the kernel.

I agree, but I think this is covered by "not changing FreeBSD versions" :)

> The reason I point this out is, when certain things in kernel-land
> change which certain programs rely upon (but haven't been recompiled to
> be aware of that change), odd things can happen.  The most "famous" of
> the bunch is when top(1) or ps(1) start failing in bizarre ways.
> 
> Thus, my point: it *probably* will work, but DO NOT assume that it will.

To be even more precise, it will probably (with very high certainty)
work for two FreeBSD versions x1.y1 and x2.y2 if x1 == x2 and y1 <= y2.
It will probably also work for any combination of y1 and y2 as long as
x1 == x2. It will probably fail if x1 != x2.

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