Installation that is performed without user interaction during its progress or with no user present at all. One of the reasons to use this approach is to automate the installation of a large number of systems. An unattended installation either does not require the user to supply anything or has received all necessary input prior to the start of installation. Such input may be in the form of command line switches or an answer file, a file that contains all the necessary parameters.
Windows XP and most Linux distributions are examples of operating systems that can be installed with an answer file. In unattended installation, it is assumed that there is no user to help mitigate errors. For instance, if the installation medium was faulty, the installer should fail the installation, as there is no user to fix the fault or replace the medium. Unattended installers may record errors in a computer log for later review.