/usr/lib/systemd/system-generators/

 /usr/lib/systemd/system-generators

cloud-init-generator
friendly-recovery
lvm2-activation-generator
netplan
postgresql-generator
snapd-generator
systemd-bless-boot-generator
systemd-cryptsetup-generator
systemd-debug-generator
systemd-fstab-generator
systemd-getty-generator
systemd-gpt-auto-generator
systemd-hibernate-resume-generator
systemd-rc-local-generator
systemd-run-generator
systemd-system-update-generator
systemd-sysv-generator
systemd-veritysetup-generator

See also

• Systemd: systemctl, systemd-journald, journalctl systemd-cat, systemd-logind, systemd-networkd:networkctl, systemd-timesyncd, systemd-resolved, systemd-udevd , Systemd-logind: loginctl, hostnamectl, udevadm, systemd-run, portablectl, systemd-nspawn, systemd resource management, Timer (systemd), systemd logs, /etc/systemd/, systemd services, systemd-mount, /run/systemd/, .service, /usr/lib/systemd/, /usr/lib/systemd/system/, /usr/lib/systemd/system/systemd-resolved.service, /lib/systemd/, machinectl, systemd-oomd, systemd-analyze

https://wiki.ubuntu.com/DebuggingSystemd