For an ordinary user on Ubuntu 18.04.1 the tab key doesn't work for a command argument.
For example, entering systemctl sta and pressing the tab doesn't produce a match for "start status".
It works for the root user. The example below is for the root user:
systemctl sta<press tab key>
start status
The above functions as expected.
However, it doesn't work for a non-root user.
systemctl sta<press tab key>
did not match any argument.
It happened after updating from 16.04 to 18.04.1.
