Scipt to generate SHA-512 password fields suitable for /etc/shadow. Requires a relatively recent version of mkpasswd.

genshadow.sh

#!/bin/bash

if [ "x$1" == 'x' ]; then
    echo "USAGE: $0 '<password>'"
    exit 1
fi

# Get an md5sum of the string for eventual extraction.
md5=$( echo $1 | md5sum )
extract="${md5:2:8}"

mkpasswd -m SHA-512 "$1" "$extract"
exit $?