In enterprise linux 7, Red Hat replaced the init bootloader with systemd.
Red Hat 5 and 6 use something called SysVinit (short for: System V init) for the boot process.
init is the first process called and loaded by the kernel, which then loads all other processes. init was a very common boot loader in linux and unix systems for a long time.
In Mac OS 10.5 and up, instead of using init they use launchd. When you load or unload a service you use “launchctl” in the command line. In Red Hat Enterprise Linux 5 & 6, instead of the mac’s launchctl you use the command “service” (‘service networking start’ for example).
In Red Hat 7, they replaced init with something called systemd. Now systemd launches first instead of init. There are a number of benefits to this, one of which is that systemd can start processes in parallel, init had to go one at a time sequentially. The downside is that there are a whole bunch of new things to learn about it.
Now, in RH 7, instead of the command “service” you use the command systemctl (i.e. “systemctl rsyslog start”)
They were smart enough to make things backwards compatible, so the “service” command will still work for us dummies, and the syntax is very similar. However, this is something to be aware of as the commands will eventually change. Best to learn it now.