From 2081905c43960871fd6db2bb032a59aec80a4417 Mon Sep 17 00:00:00 2001 From: Alex Gronenwoud Date: Thu, 5 Feb 2004 22:17:48 +0000 Subject: Simplifying the second copying of the kernel headers. git-svn-id: http://svn.linuxfromscratch.org/LFS/trunk/BOOK@3229 4aa44e1e-78dd-0310-a6d2-fbcd4c07a689 --- chapter06/kernel-headers.xml | 74 ++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 74 insertions(+) create mode 100644 chapter06/kernel-headers.xml (limited to 'chapter06/kernel-headers.xml') diff --git a/chapter06/kernel-headers.xml b/chapter06/kernel-headers.xml new file mode 100644 index 000000000..14d73d992 --- /dev/null +++ b/chapter06/kernel-headers.xml @@ -0,0 +1,74 @@ + +Installing Linux-&kernel-version; headers + + +&buildtime; &kernel-time-headers; +&diskspace; &kernel-compsize-headers; + +   + + +Installation of the kernel headers + +We won't be compiling a new kernel yet -- we'll do that when we have +finished the installation of all the packages. But the libraries installed in +the next section need to refer to the kernel header files in order to know how +to interface with the kernel. Instead of unpacking the kernel sources again, +making the version file and the symlinks and so on, we will simply copy the +headers from the temporary tools directory in one swoop: + +cp -a /tools/include/{asm,asm-generic,linux} /usr/include + +A few kernel header files refer to the autoconf.h +header file. Since we have not yet configured the kernel, we need to create +this file ourselves in order to avoid a compilation failure of Sysklogd. +Create an empty autoconf.h file with: + +touch /usr/include/linux/autoconf.h + + + +   + + +Why we copy the kernel headers + +In the past it was common practice to symlink the +/usr/include/{linux,asm} directories +to /usr/src/linux/include/{linux,asm}. +This was a bad practice, as the following extract from a +post by Linus Torvalds to the Linux Kernel Mailing List points out: + +I would suggest that people who compile new kernels should: + + - not have a single symbolic link in sight (except the one that the + kernel build itself sets up, namely the "linux/include/asm" symlink + that is only used for the internal kernel compile itself) + +And yes, this is what I do. My /usr/src/linux still has the old 2.2.13 +header files, even though I haven't run a 2.2.13 kernel in a _loong_ +time. But those headers were what Glibc was compiled against, so those +headers are what matches the library object files. + +And this is actually what has been the suggested environment for at +least the last five years. I don't know why the symlink business keeps +on living on, like a bad zombie. Pretty much every distribution still +has that broken symlink, and people still remember that the linux +sources should go into "/usr/src/linux" even though that hasn't been +true in a _loong_ time. + +The essential part is where Linus states that the header files should be +the ones which Glibc was compiled against. These are +the headers that should be used when you later compile other packages, as they +are the ones that match the object-code library files. By copying the headers, +we ensure that they remain available if later you upgrade your kernel. + +Note, by the way, that it is perfectly all right to have the kernel sources +in /usr/src/linux, as long as you don't +have the /usr/include/{linux,asm} +symlinks. + + + + + -- cgit v1.2.3-54-g00ecf