/usr/lib/systemd/system-generators/systemd-sysv-generator
systemd-sysv-generator is a generator that creates wrapper .service units for m[blue]SysV initm[][1] scripts in /etc/init.d/* at boot and when configuration of the system manager is reloaded. This will allow systemd(1) to support them similarly to native units.
m[blue]LSB headersm[][2] in SysV init scripts are interpreted, and the ordering specified in the header is turned into dependencies between the generated unit and other units. The LSB facilities "$remote_fs", "$network", "$named", "$portmap", "$time" are supported and will be turned into dependencies on specific native systemd targets. See systemd.special(7) for more details.
SysV runlevels have corresponding systemd targets (runlevelX.target). The wrapper unit that is generated will be wanted by those targets which correspond to runlevels for which the script is enabled.
systemd does not support SysV scripts as part of early boot, so all wrapper units are ordered after basic.target.
systemd-sysv-generator implements systemd.generator(7).
systemd(1), systemd.service(5), systemd.target(5)