1 | <sect2><title> </title><para> </para></sect2>
|
---|
2 |
|
---|
3 | <sect2>
|
---|
4 | <title>Why we copy the kernel headers and don't symlink them</title>
|
---|
5 |
|
---|
6 | <para>In the past it was common practice to symlink the
|
---|
7 | <filename class="directory">/usr/include/{linux,asm}</filename> directories
|
---|
8 | to <filename class="directory">/usr/src/linux/include/{linux,asm}</filename>.
|
---|
9 | This was a <emphasis>bad</emphasis> practice, as the following extract from a
|
---|
10 | post by Linus Torvalds to the Linux Kernel Mailing List points out:</para>
|
---|
11 |
|
---|
12 | <screen>I would suggest that people who compile new kernels should:
|
---|
13 |
|
---|
14 | - not have a single symbolic link in sight (except the one that the
|
---|
15 | kernel build itself sets up, namely the "linux/include/asm" symlink
|
---|
16 | that is only used for the internal kernel compile itself)
|
---|
17 |
|
---|
18 | And yes, this is what I do. My /usr/src/linux still has the old 2.2.13
|
---|
19 | header files, even though I haven't run a 2.2.13 kernel in a _loong_
|
---|
20 | time. But those headers were what glibc was compiled against, so those
|
---|
21 | headers are what matches the library object files.
|
---|
22 |
|
---|
23 | And this is actually what has been the suggested environment for at
|
---|
24 | least the last five years. I don't know why the symlink business keeps
|
---|
25 | on living on, like a bad zombie. Pretty much every distribution still
|
---|
26 | has that broken symlink, and people still remember that the linux
|
---|
27 | sources should go into "/usr/src/linux" even though that hasn't been
|
---|
28 | true in a _loong_ time.</screen>
|
---|
29 |
|
---|
30 | <para>The essential part is where Linus states that the header files should be
|
---|
31 | <emphasis>the ones which glibc was compiled against</emphasis>. These are
|
---|
32 | the headers that should be used when you later compile other packages, as they
|
---|
33 | are the ones that match the object-code library files. By copying the headers,
|
---|
34 | we ensure that they remain available if later you upgrade your kernel.</para>
|
---|
35 |
|
---|
36 | <para>Note, by the way, that it is perfectly all right to have the kernel sources
|
---|
37 | in <filename class="directory">/usr/src/linux</filename>, as long as you don't
|
---|
38 | have the <filename class="directory">/usr/include/{linux,asm}</filename>
|
---|
39 | symlinks.</para>
|
---|
40 |
|
---|
41 | </sect2>
|
---|
42 |
|
---|