Create the application directory structure:

sudo mkdir -p /opt/atlassian/confluence/
sudo mkdir /opt/atlassian/confluence/confluence-home-docs
sudo mkdir /opt/atlassian/confluence/confluence-home-help

Download and extract the Confluence application:

wget https://www.atlassian.com/software/confluence/downloads/binary/atlassian-confluence-5.7.5-x64.bin
wget https://www.atlassian.com/software/confluence/downloads/binary/atlassian-confluence-5.7.5.tar.gz
tar -xzvf atlassian-confluence-5.7.5.tar.gz
sudo mv atlassian-confluence-5.7.5 /opt/atlassian/confluence/

Add the Confluence user to run the instance:

sudo adduser confluence

Give the Confluence user permissions to the application directories:

sudo chown -R confluence:confluence /opt/atlassian/confluence/confluence-home-docs
sudo chown -R confluence:confluence /opt/atlassian/confluence/confluence-home-help
sudo chmod -R 775 /opt/atlassian/confluence/confluence-home-docs
sudo chmod -R 775 /opt/atlassian/confluence/confluence-home-help

Install the Java Runtime Environment (Java JRE):

sudo apt-get install default-jre

Edit confluence-init.properties; specify confluence.home as specified below:

sudo vi /opt/atlassian/confluence/atlassian-confluence-5.7.5/confluence/WEB-INF/classes/confluence-init.properties

Set the confluence.home attribute:

confluence.home=/opt/atlassian/confluence/confluence-home-docs

Start Confluence:

sudo /opt/atlassian/confluence/atlassian-confluence-5.7.5/bin/start-confluence.sh