Install GeoServer on Ubuntu 18.04

geoserver-install.sh

#
 sudo su 
 apt-get install openjdk-8-jre 

# PostgreSQL and PostGIS
 apt-get install postgresql postgresql-contrib postgis postgresql-10-postgis-2.4

# Create "geoserver" database
sudo -u postgres createuser -P geoserver
sudo -u postgres createdb -O geoserver geoserver
sudo -u postgres psql -c "CREATE EXTENSION postgis; CREATE EXTENSION postgis_topology;" geoserver

# GeoServer install
apt install unzip
mkdir -p /var/www/geoserver
cd /var/www/geoserver
wget https://netcologne.dl.sourceforge.net/project/geoserver/GeoServer/2.15.2/geoserver-2.15.2-bin.zip
unzip geoserver-2.15.2-bin.zip

mv geoserver-2.15.2/* .
echo "export GEOSERVER_HOME=/var/www/geoserver" >> ~/.profile
. ~/.profile

# GeoServer run
./bin/startup.sh

#In the browser open http://localhost:8080/geoserver/web/

#Default username and password is admin and geoserver 

Updated GeoServer for version 2.15.2 binary

Added in the begging sudo su