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Date:      Sat, 10 Jan 1998 19:50:48 +1030
From:      Greg Lehey <grog@lemis.com>
To:        Jason Wells <jcwells@u.washington.edu>
Cc:        freebsd-questions@FreeBSD.ORG
Subject:   Re: LKM versus Static Kernel
Message-ID:  <19980110195048.17940@lemis.com>
In-Reply-To: <3.0.3.32.19980104175505.007cc9b0@jcwells.deskmail.washington.edu>; from Jason Wells on Sun, Jan 04, 1998 at 05:55:05PM %2B0000
References:  <3.0.3.32.19980104175505.007cc9b0@jcwells.deskmail.washington.edu>

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On Sun, Jan 04, 1998 at 05:55:05PM +0000, Jason Wells wrote:
> I was considering adding Linux compatibility to my system. After looking
> thru the handbook, I noticed that this can be done as a loadable kernel
> module. I looked in the lkm directory and noticed the linux object file.
>
> Why is using an lkm better than using a statically compiled kernel? Vice
> versa? What are the issues at stake?

Strange that nobody has answered this message.

I don't see any important disadvantages in loadable kernel modules; in
fact, it's my preferred method of implementing additional
functionality.  Briefly,

Pro:

1.  LKMs are modular.  You can load them or not load them, and you
    don't need to rebuild the kernel to add their functionality.

2.  You only need to have an LKM loaded when you want to run it.  If
    you want, you can unload it and reclaim the memory it occupies.

3.  Starting the system can be faster, since you don't need to
    initalize the kernel version of the LKM.

Con:

1.  Although they're separate, LKMs are part of the kernel, and they
    must match the release.  If you try to run a 2.2.2 release LKM
    with release 2.2.5, you could have trouble, including panics, or
    it might not work at all.

I'm sure there are more; if anybody wants to, feel free to add to this
list.

Greg



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