[gentoo-dev] Ebuilds referencing /usr/src/linux makes baby Jesus kill kittens

[Ciaran McCreesh <ciaranm@gentoo.org>]

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Just a friendly reminder that you should really avoid messing around
with /usr/src/linux inside ebuilds. In particular, code like the
following is utterly wrong:

if [ ! -e "/usr/src/linux/include/linux/dm-ioctl.h" ] ; then
        eerror
        eerror "Your currently linked kernel (/usr/src/linux) hasn't"   
        eerror "been patched for device mapper support."               
        eerror
        die "kernel not patched for device mapper support"       
fi

Don't try to do clever things with /usr/src/linux to determine whether a
kernel has a particular feature. Especially don't go near .config. The
kernel running may not be the kernel in /usr/src/linux. The box in
question might be a chroot setup or a netboot system or a system built
with a crosscompiler, in which case /usr/src/linux* won't exist at all.
The user might be sharing kernel binaries between dozens of identical
boxes and only building on one. The user might be building kernels
in/home to avoid having to build kernels as root or chown a bunch of
stuff. The /usr/src/linux symlink might be out of date. The box might be
building binary packages for a different system.

You shouldn't be using /usr/src/linux for headers either. I suggest
people give the following a good read before they commit even more
broken code to the tree:

http://www.linuxmafia.com/faq/Kernel/usr-src-linux-symlink.html

Think of the kittens, people!

-- 
Ciaran McCreesh : Gentoo Developer (Sparc, MIPS, Vim, Fluxbox)
Mail            : ciaranm at gentoo.org
Web             : http://dev.gentoo.org/~ciaranm


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