Disable ipv6 on Ubuntu

There is a strange problem with kernel message: lo: Disabled Privacy Extensions
It is caused by the ipv6 module in kernel.
reference:
Old Nabble - ubuntu-users - lo: Disabled Privacy Extensions

To close it, you have to recompile kernel.
There is a hack to close it through the loader. (If no ipv6 needed)
edit the /etc/default/grub and modify:
GRUB_CMDLINE_LINUX="ipv6.disable=1"

here are the references to close it:
1. Ubuntu Tips - JoeHacker
2. Grub 2 - Ubuntu Wiki