Ubuntu change hostname script

change_host_name.sh

if [ ! -n "$1" ] 
then
    echo 'Missed argument : hostname'
    exit 1
fi

if [ "$(id -u)" != "0" ]; then
	echo "Sorry, you are not root."
	exit 1
fi

hostname $1
chmod 777 /etc/hostname /etc/hosts
sed "s/template/$1/g" /etc/hosts > /home/user/hosts.out
rm /etc/hosts
mv /home/user/hosts.out /etc/hosts
echo "$1" > /etc/hostname
chmod 644 /etc/hostname /etc/hosts
service hostname down
service hostname start
dhclient

DO NOT RUN THE ABOVE SCRIPT!!! The below script was tested on Ubuntu 16.04 several times with no issues.

#!/bin/bash

if [ ! -n "$1" ] ; then
	echo 'Missing argument: new_hostname'
	exit 1
fi

if [ "$(id -u)" != "0" ] ; then
	echo "Sorry, you are not root."
	exit 2
fi

CUR_HOSTNAME=$(cat /etc/hostname)
NEW_HOSTNAME=$1

# Display the current hostname
echo "The current hostname is $CUR_HOSTNAME"

# Change the hostname
hostnamectl set-hostname $NEW_HOSTNAME
hostname $NEW_HOSTNAME

# Change hostname in /etc/hosts & /etc/hostname
sudo sed -i "s/$CUR_HOSTNAME/$NEW_HOSTNAME/g" /etc/hosts
sudo sed -i "s/$CUR_HOSTNAME/$NEW_HOSTNAME/g" /etc/hostname

# Display new hostname
echo "The new hostname is $NEW_HOSTNAME"