Add a user, with a home directory but without shell access, to the Samba and Time Machine services

addmediauser.sh

#!/bin/sh
# Call this script as root like:
#     ./addmediauser.sh myusername mypassword
# Password will be shown in plain text (obviously)
# so watch out for shoulder surfers!

USERNAME=$1
PASSWORD=$2

useradd --create-home --groups samba timemachine --shell /bin/false $USERNAME
echo "$USERNAME:$PASSWORD" | sudo chpasswd
(echo $PASSWORD; echo $PASSWORD) | smbpasswd -as ${USERNAME}