I have compiled a smaller kernel for my system a couple of times, and I've had good luck with it most of the time, but I've never done anything with the system.map file.

I saw this helpful and friendly link on the Linux Questions forum, describing how to recompile a kernel in SlackWare, but he just said to copy the system.map file without mentioning what it does. Am I missing something valuable?

http://en.wikipedia.org/wiki/System.map

Jfgi

You most likely won't ever need it so there is no harm in not copying it over. On the otherhand, it's about 700K so why wouldn't you? Make install copies it btw.

System.map is used by syslogd/klogd for logging the kernel. They look respectively on /, /boot and /lib/modules/`uname -r`/build to find out a proper System.map. They are able to determine automagically the correct version of System.map, so you can have several files around without hurting the system. (it is not necessary you append the kernel version to the file name)
So..it is not strickly necessary you copy it to /boot ('though it doesn't hurt) if you have the kernel sources installed.
In case of lack of a proper System.map you just have problems in case of kernel crash or segfault as you have no logs to check.
System map is also used by some emulators/virtual machines, so if you use one you'd better go with System.map at the right place (usually /boot).
Ciao

Why do I always seem to forget Wikipedia as a potential source of technical knowledge? I just don't know.

Thank you both for your sharing your valuable knowledge.

-dP

The system.map file is a mapping between hexadecimal symbols used by the kernel into human readable function and variable names. As these symbols change with every kernel compile, a new system.map is generated each time.

Unless you are doing crash dump analysis and debugging, I wouldn't worry too much about this file. Just make it good practice to copy the new one to /boot each time you replace your kernel.

--Aleks