LKMPG is now maintained at GitHub (#5473)

The Linux Kernel Module Programming Guide (LKMPG) is now maintained and
updated for Linux v5.x in collaboration with community members.

books/free-programming-books.md

@@ -2054,7 +2054,7 @@ Kerridge (PDF) (email address *requested*, not required)
 * [The Debian Administrator's Handbook](https://debian-handbook.info)
 * [The Linux Command Line](http://linuxcommand.org/tlcl.php) (PDF)
 * [The Linux Development Platform](http://ptgmedia.pearsoncmg.com/imprint_downloads/informit/perens/0130091154.pdf) (PDF)
-* [The Linux Kernel Module Programming Guide](http://tldp.org/LDP/lkmpg/2.6/html/)
+* [The Linux Kernel Module Programming Guide](https://sysprog21.github.io/lkmpg/)
 * [The Linux System Administrator's Guide](http://www.tldp.org/LDP/sag/html/index.html)
 * [Ubuntu Pocket Guide and Reference](http://www.ubuntupocketguide.com/index_main.html)
 * [Ubuntu Server Guide](https://help.ubuntu.com/16.04/serverguide/serverguide.pdf) (PDF)