Raspbian - Change Default User Name

change-username.sh

#!/bin/bash
##############################################################################
# Works for me with clean and fully updated Rasbian Jessie on Rasberry Pi 2b #
# ONLY USE THIS SCRIPT If YOU KNOW WHAT YOU ARE DOING - RUN AT YOUR OWN RISK #
# MUST BE RUN AS ROOT FROM A COMMAND LINE LOGIN - DO NOT RUN AS SUDO USER    #
##############################################################################

echo "Change username?"
select yn in "Yes" "No"; do
    case $yn in
        Yes )
            echo -n "Enter old user name: ";
            read oldname;
            echo -n "Enter new user name: ";
            read newname;

            # Test if old user name exists
            test1=$(cut -d: -f1 /etc/passwd|grep ^"$oldname")
            if [ -z "$test1" ] ; then
                echo -e "The old user name '$oldname' does not exist.\nDid you enter it correctly?"
                exit
            fi

            # Test if old user name has any running processes
            test2=$(ps aux|grep ^"$oldname")
            if [ -n "$test2" ] ; then
                echo -e "The old user name '$oldname' still has running processes.\nStop the processes before running again.\n"
                ps aux|grep ^"$oldname"
                exit
            fi

            #Test if new user name already exits
            test3=$(cut -d: -f1 /etc/passwd|grep ^"$newname")
            if [ -n "$test3" ] ; then
                echo -e "The new user name '$newname' already exists.\nDid you enter it correctly?"
                exit
            fi

            # Modify username and home directory
            usermod -l $newname -d /home/$newname -m $oldname;

            # Modify groupname
            groupmod -n $newname $oldname;

            # Modify /usr/bin/raspi-config
            filename=/usr/bin/raspi-config;
            sed $filename -i -e "s/passwd "$oldname"/passwd "$newname"/";
            sed $filename -i -e "s/login -f "$oldname" tty1/login -f "$newname" tty1/";
            sed $filename -i -e "s/autologin-user="$oldname"/autologin-user="$newname"/";
            sed $filename -i -e "s/id -u "$oldname"/id -u "$newname"/";
            sed $filename -i -e "s/default user ("$oldname")/default user ("$newname")/";

            # Modify /etc/lightdm/lightdm.conf
            sed /etc/lightdm/lightdm.conf -i -e "s/autologin-user="$oldname"/autologin-user="$newname"/";

            # Modify /etc/sudoers
            sed /etc/sudoers -i -e "s/"$oldname" ALL=(ALL) NOPASSWD: ALL/"$newname" ALL=(ALL) NOPASSWD: ALL/";

            # Modify /etc/systemd/system/autologin@.service (credit to AndyD on Raspberry Pi forums)
            sed /etc/systemd/system/autologin@.service -i -e "s/autologin "$oldname"/autologin "$newname"/";

            break;;
        No )
            break;;
    esac
done

echo "Script completed successfully."

exit