"reboot" or "shutdown -r now": what restart command is safer?
Shutdown is preferable because it allows you to specify the reason for the drastic action -- something you should always do. The message will be recorded in the log(s) for posterity. For example:
shutdown -r now 'Kernel upgrade requires reboot'
You can also perform a scheduled reboot -- by specifying something other than
now as the reboot time:
shutdown -r 22:00 'Work around kernel memory leak'
Then your users will get periodic reminders to get out and so on -- the process will be more orderly and professional.
For Red Hat systems, there is no functional difference between
shutdown -r now.
Do whatever is easier for you.
If you take a look, in RHEL 7 both
/sbin/reboot are actually just symlinks to systemd's
systemctl command. So, use whatever you want. No functional difference as ewwhite told, not even in earlier RHEL releases which did not yet use systemd.
reboot is safer.
reboot your intent is clear and there is no way to mistype it for something else like
shutdown -t now which could leads to a few headache if you are using on a remote server with limited control.