Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!usc!wuarchive!uunet!bcstec!iftccu!bressler
From: bressler@iftccu.ca.boeing.com (Rick Bressler)
Newsgroups: comp.unix.admin
Subject: Re: installing new kernels
Message-ID: <5690001@iftccu.ca.boeing.com>
Date: 10 Jun 91 20:10:40 GMT
References: <2534@sud509.ed.ray.com>
Organization: Boeing Commercial Airplane Group
Lines: 23

Bill Heiser - Unix Sys Admin writes in part:

>I've always been under the impression that a machine should be
>in single user mode before installing a new kernel.  As such,
>I've always brought the machine down before removing /unix and
>installing the new version there.
>

Well, one day, in a moment of brain lock, I actually did this.  All sorts of
weird things started happening.  I'm no wizard, but from the symptoms, I 
expect that at a minimum, many routines look at the object to find offsets
to various variables in the kernel.  When you change the kernel, the offsets
no longer match the copy in memory....

It didn't take me long to realize that I'd forgotten to get to single 
user, so I have no idea what would have broken in the long run.  I know 
vmstat and similar stuff didn't work.  No file systems were corrupted, but
as I said, it was sort of an OH S**t situation, and I didn't leave it running
for more than a couple of minutes.

I'd recommend not trying it.  The system in question was a BSD 4.3 system. 

Rick.