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From: John Baldwin <jhb@freebsd.org>
To: freebsd-hackers@freebsd.org,
 Devin Teske <dteske@freebsd.org>
Subject: Re: disadvantages of running 8.3 kernel on freebsd 8.2 system
Date: Thu, 17 Jan 2013 11:03:40 -0500
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 (bigwig.baldwin.cx); Thu, 17 Jan 2013 13:40:54 -0500 (EST)
Cc: Ali Okan =?windows-1252?q?Y=DCKSEL?= <kaox.gen@gmail.com>
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On Thursday, January 17, 2013 10:57:01 am Devin Teske wrote:
> On Jan 17, 2013, at 4:06 AM, Ali Okan Y=DCKSEL wrote:
>=20
> > I know for UPDATING, it s not correct way, but i tried and 8.2 system=20
works
> > with 8.3 kernel (copied 8.3 /boot/kernel directory to freebsd 8.2
> > /boot/kernel) and it s not good solution but i want to know;
> >=20
> >=20
> >   - What are specific disadvantages that i can see clearly, running 8.3
> >   kernel on freebsd 8.2?
>=20
> A couple user land tools might barf on you (listed below).
>=20
> Other than that, it's generally considered very safe.
>=20
> The quintessential test-case is running an 8.2 jail under an 8.3 host.
>=20
> We do this all the time with various releases (again, most-problematic=20
utilities listed below).
>=20
>=20
>=20
> >   - What are user land tools those not match with 8.3 kernel on freebsd
> >   8.2 system=85?
> >=20
>=20
> top and ps might complain about procsize mismatch.
>=20
> netstat has been known to have problems if the gap is too wide.

These generally do not have problems in recent release branches.  top and p=
s=20
haven't complained about procsize since the 4.x days as 5.0 introduced a ne=
w=20
kinfo_proc structure that the kernel exports and it hasn't changed in size=
=20
since 5.0.

The mfiutil issue dhw@ mentioned is real and is due to an mfi(4) driver=20
change.  I merged a fix for the panics to 8-stable, but it just makes
old mfiutil binaries not work at all.

=2D-=20
John Baldwin