What script are you using? SAFEHOSTNAME sounds like a placeholder for your real host name as specified in the entries in your sudoers file. (visudo).
Be careful when picking up information from old threads, this one was started in 2017, a lot has changed since then. Old threads are a great resource but don't blindly use code without checking compatibility with your current system.
The FusionPBX installer now puts a couple of maintenance jobs in /etc/cron.daily/ Have a look at them.
I generally delete the jobs in /etc/cron.daily/ because I prefer to run my own jobs and at specific times of the day, but the default jobs work well and are a good reference source for those new to Fusion.