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From: "J.Smith" <lbalbalba@hotmail.com>
Newsgroups: comp.os.linux.misc,comp.os.linux.development
Subject: Re: What is a system map, part 2?
Date: Sun, 15 Oct 2000 17:44:51 +0200
Message-ID: <8scj8t$hku$1@spectra.a2000.nl> 
References: <39E6F83C.63A36E54@exit109.com> 
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Oh boy, here we go again... :)

For the viewers that have just tuned in, there was a tread on
comp.os.linux.misc not so long ago that discussed the need for and use of
the /boot/System.map file. There also seemed to be some confusion about how
to handle 2 different kernel's in /boot, and the two different
/boot/System.map files that go with it.

Although there was no conclusive evidence, the current status seems to be as

System.map is a "map" of your kernel. It contains info about the entry
points of the functions you compiled into your kernel, and de-bug
information. The kernel itself knows the addresses and entry-points, but
that file is needed for some programs which need info about kernel entry
points. These programs are klogd(8), ksymoops(8), depmod(8), and the procps
tools (ps(1), top(1), ...).  These programs don't all do the same thing in
looking for System.map files. depmod(8) doesn't need a System.map file if
it's operating on the currently running kernel. ps(1) and klogd(8) like to
find a System.map file, but don't look in the same places.

You may have noticed that I have taken the liberty of cross-posting this
message to os.linux.development. Although this may seem a little bit odd, or
off-topic for this newsgroup, but I guess that the only people who can
really clarify what system.map is used for and how you should handle two
kernels&map files are the guys who actually know something about the
source-code :)


> All this talk about the "system.map" file prompted me to look
> at my directory, /boot.
> I guess my question is: does anyone (i.e., any process,
> including the kernel) use these symbolic links? Because if so,
> I should change them to point to the kernel I normally use. But
> that raises another question: If I boot a different kernel,
> perhaps because I installed one that is no good as the latest
> one, I will get the wrong values for the symbolic links. What
> are the consequences of this?

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