> dhclient's /sbin/dhclient-script uses sed.  Sed is in /usr/bin, and hence
> is available if and only if /usr is mounted.  But /usr is mounted by
> mountcritremote, and dhclient (correctly) requires mountcritlocal.  This
> strikes me as a bug...

If this is the line in question:

     arp -n -a | sed -n -e 's/^.*(\(.*\)) at .*$/arp -n -d \1/p' | sh

I may as well point out that, in addition, arp is in /usr/sbin.