Jan Danielsson wrote:
>    Now that I started writing this stuff again, I believe that the
> problem I had before was in fact that "sed" is in "/usr/bin", but /usr
> hasn't been mounted when dhclient-enter-hook is run the first time
> (during boot).

I'm not aware of any reasons to put /usr on a different partition than /.
There may be historical ones like tiny disks or whatever.

-- 
Christian