Where are SYSTEMD units created at runtime typically stored?

SYSTEMD units created at runtime are typically stored in the /run/systemd/system directory. This directory is used for runtime-generated unit files that are created by the system or by services during runtime. These units are temporary and exist only while the system is running, meaning they will not persist across reboots.

In contrast, the other options refer to directories that hold unit files that are part of the system at a more permanent level. The /etc/systemd/system directory is meant for user-defined units and overrides to ensure custom configurations persist through reboots. The /lib/systemd/system and /usr/lib/systemd/system directories contain the default unit files provided by installed packages, which also remain static and persistent.

Therefore, the most appropriate location for SYSTEMD units that are generated and utilized at runtime is /run/systemd/system, as it is specifically designated for this purpose.