We use sessions to save data during the installation process. You'll need to change permissions to 777 in your installation for
in Linux this is easy. From the command line (or SSH terminal), type:
cd ~/public_html/installer/application/cache/ && chmod 777 sessions. Note: the path to your cache folder may be different.
Most hosting control panels have a 'File Manager' which will allow you to change permissions for files and folders.