Get Linux kernel Souce Code

1. use wget (you could get any version you want):

$ wget http://www.kernel.org/pub/linux/kernel/v2.6/linux-2.6.18.3.tar.bz2
or

$ wget http://www.kernel.org/pub/linux/kernel/v2.6/linux-2.6.18.tar.gz

2. use git

$ git clone git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux-2.6.git

$ cd linux-2.6

$ git reset --hard v2.6.17 /* Change current branch to 2.6.17 */

more details: http://www.kernel.org/pub/software/scm/git/docs/user-manual.html