That's what /etc/rc.local
is for. Here's an example:
$ cat /etc/rc.local
# This script will be executed *after* all the other init scripts.
# You can put your own initialization stuff in here if you don't
# want to do the full Sys V style init stuff.
# Activate and mount all available volume groups with mount points in /etc/fstab
# Mount any "noauto" devices listed in /etc/fstab that are not already mounted