Symbolic and hard link and Rsync

http://tuyetkiem.wordpress.com/2009/03/30/hardlink-symlink/
http://projektantos.wordpress.com/2009/06/01/hard-link-vs-symbolic-link/
http://securityforall.wordpress.com/2012/06/24/symbolic-linksymlink-va-hard-link-lien-ket-cung-va-lien-ket-mem/
http://dev.mysql.com/doc/refman/5.1/en/symbolic-links-to-tables.html

Rsync
http://www.nhatnghe.com/forum/showthread.php?t=28564
http://linux.about.com/library/cmd/blcmdl1_rsync.htm
http://www.tutorialspoint.com/unix_commands/rsync.htm
http://redmine.9store.vn/issues/192