Change Ubuntu hostname

change_ubuntu_hostname.sh

#!/bin/bash
#
# Change hostname for Ubuntu host

OLD_NAME=$(hostname)
echo "- Current hostname is: $OLD_NAME"
read -p "- Please input new hostname: " NEW_NAME

update_ect_hostname() {
    sudo hostname $NEW_NAME
    sudo bash -c "echo $NEW_NAME > /etc/hostname"
}

update_etc_hosts() {
    # Insert the line "127.0.1.1 <host_name>"" into /etc/hosts
    is_configured=$(grep -E "127.0.1.1.*$NEW_NAME" /etc/hosts)
    if [ "$is_configured" = "" ]; then
        is_set_with_other_name=$(grep -E "127.0.1.1" /etc/hosts)
        if [ "$is_set_with_other_name" = "" ]; then
            sudo sed -i "2i127.0.1.1 $NEW_NAME" /etc/hosts
        else
            sudo sed -i "s/^127.0.1.1.*$/127.0.1.1 $NEW_NAME/g" /etc/hosts
        fi
    fi
}

if [ $NEW_NAME = "" ]; then
    echo "- Please enter the new hostname!!"
    exit 1
fi

echo "- Updating with new hostname: $NEW_NAME"
update_etc_hosts
update_ect_hostname

echo "- Current hostname is: $(hostname)"
echo "--- DONE ---"