Autocompletion doesn't work while logged as root

In Debian:

Check your /root/.bashrc file for these lines

if [ -f /etc/bash_completion ]; then
  . /etc/bash_completion
fi

If they do not exist add them to the end of the file using your favorite text editor.

In CentOS:

# yum install bash-completion

How do I use bash Autocomplete feature?

Then exits a login shell / ssh session and log back in using the following command:
# logout
Open a terminal or log in using ssh:
$ ssh [e-mail]
Alternatively, use the following command to source completion code for bash:
$ . /etc/bash_completion
OR
$ source /etc/bash_completion