11.1 Understanding Ubuntu systemd Targets

Ubuntu can be configured to boot into one of a number of states (referred to as targets), each of which is designed to provide a specific level of operating system functionality. The target to which a system will boot by default is configured by the system administrator based on the purpose for which the system is being used. A desktop system, for example, will most likely be configured to boot using the graphical user interface target, while a cloud-based server system would be more likely to boot to the multi-user target level.

During the boot sequence, a process named systemd looks in the /etc/systemd/system folder to find the default target setting. Having identified the default target, it proceeds to start the systemd units associated with that target so that the system boots with all the necessary processes running.

For those familiar with previous Ubuntu versions, systemd targets are the replacement for the older runlevel system...