Aliasing users

[nyarlathotep]

How do I make two users with the same uid? This was always easy to do under Linux, are there any caveots under Mac OS X?

[gatorparrots]

#!/bin/sh

##
# addalias
# This script will create aliases entries in NetInfo
# author: gatorparrots <gatorparrots@mad.scientist.com>
#
# usage: addalias [username] [alias]
# [alias] can be a local user account or an e-mail address
##

username=$1
alias=$2

if [ $# -eq 0 ]; then
  printf "usage: addalias [username] [alias]\n"
  printf "[alias] can be a local user account or an e-mail address\n" >&2
  exit 2
fi

# Need to be a sudoer to add aliases
sudo -p "Please authenticate to add alias (administrator password): " printf "" || {
	echo "Abort: could not authenticate" >&2
	exit 1
}
if [ -z "`niutil -read . /aliases/$alias 2> /dev/null `" ]; then
    sudo niutil -create . /aliases/$alias
    sudo niutil -createprop . /aliases/$alias members $username
    echo "Alias created"
else
    sudo niutil -appendprop . /aliases/$alias members $username
    echo "Alias added"
fi
echo "$alias --> $username"
niutil -read . /aliases/$alias

[nyarlathotep]

That would just be an email alias, no? I wanted a full "login alias," same uid, diffrent login names.
Jeff