However, you cannot move a directory into itself. So, try "mv /opt/
local /opt/local-old"

Alternately, you could build MacPorts from source and use "./
configure --prefix=/somewhere/else" to tell MacPorts not to use /opt/
local but a different prefix of your choosing. But it might be
clearer if you just move your existing /opt/local away and let
MacPorts use its defaults.