Description: The ‘default target’ in the context of operating systems refers to the state or runlevel that the system boots into by default. This concept is fundamental in managing services and processes that start when a system is powered on. In ‘init’-based systems, the default target is associated with runlevels, which are numbers from 0 to 6, each representing a specific state of the system, such as user mode, maintenance mode, or shutdown. On the other hand, in systems using ‘systemd’, the default target is defined through target units, which are more flexible and allow for finer management of services. These targets can include ‘graphical.target’ for desktop environments or ‘multi-user.target’ for systems without a graphical interface. The ability to set a default target allows system administrators to customize boot behavior, optimizing performance and functionality according to the specific needs of the environment. Furthermore, the concept of default target is crucial for service management, as it determines which processes start automatically, thus affecting the availability and performance of the system from the moment it is powered on.
History: The concept of ‘default target’ originated with the ‘init’ system, which was the first init system used in Unix and its derivatives. Over time, as the needs of operating systems evolved, alternatives like ‘systemd’ were introduced in 2010, offering a more modern and efficient way to manage system boot and services. ‘systemd’ replaced the runlevel model with the target model, allowing for greater flexibility and control over the services that start.
Uses: The default target is primarily used in operating system configuration to determine which services and processes start automatically when the system boots. This is especially useful in servers, where specific targets can be set to optimize performance and security. It is also used in development and testing environments to quickly configure the system state according to user needs.
Examples: An example of using the default target is in a web server that boots into ‘multi-user.target’, allowing network and database services to start automatically without a graphical interface. Another example is a desktop environment that uses ‘graphical.target’, where the window manager and other graphical services automatically start when the system boots.
