View source for Legacy INIT vs systemd

Preamble
SysVinit (before Enterprise 7) was the standard init scripts & init structure everyone has gotten familiar with, using service & chkconfig commands, with Enterprise 7 we have systemd which no longer uses the traditional init scripts or SysVinit init script location, and uses the systemctl command

===  Init Scripts Locations ===
(existing ones are good examples for creating new ones)
 SysVinit:
 /etc/init.d/ - the actual init scripts
 /etc/rc.d/rc#.d/ - # for the different run levels, having symlinks to the actual init scripts in /etc/init.d/

systemd:
 /usr/lib/systemd/system/ - for system/OS related config files (analogous to init scripts)
 /etc/systemd/system/ & /etc/systemd/system/*/ - symlinks to the actual init scripts (there are no "run levels" per se, at least not "run level" numbers)
 /run/systemd/system/ - temporary runtime generated scripts (overrides system scripts)
 /etc/systemd/user/ - user created scripts (overrides runtime scripts)

===  Quick Reference ===
(.service is optional, and is assumed)
 # systemctl status name[.service]
 # systemctl enable name[.service]
 # systemctl disable name[.service]
 # systemctl start name[.service]
 # systemctl stop name[.service]
 # systemctl restart name[.service]
 # systemctl reload name[.service]
 # systemctl is-active name[.service]
 # systemctl list-units --type service --all
 # systemctl list-units --type target --all
 # systemctl get-default
 # systemctl set-default graphical.target

===  systemd Logging ===