systemd-system-update-generator - Generator for redirecting boot to offline update mode

       systemd-system-update-generator is a generator that automatically redirects the boot process to
       system-update.target, if /system-update or /etc/system-update exists. This is required to implement the
       logic explained in the systemd.offline-updates(7).

       systemd-system-update-generator implements systemd.generator(7).

       systemd-system-update-generator - Generator for redirecting boot to offline update mode

systemd(1), systemd.special(7)

systemd 257.7                                                                 SYSTEMD-SYSTEM-UPDATE-GENERATOR(8)

/usr/lib/systemd/system-generators/systemd-system-update-generator