Comment 4 for bug 15051

-P is too valuable to miss (since the rest of the world uses that perl regexp syntax)

Proposed fix (without breaking boot):

By default, in ubuntu, /usr/bin preceded /bin in the path. So install grep without -P (no libpcre) in /bin during boot.

Then install grep with -P (with libpcre) in /usr/bin, once /usr is mounted.