In macOS 10.13, Apple has removed the telnet command Telnet. The NC command is available though. This article from HCS Technology Group explains further.
A time-honored step for troubleshooting Macs. Done by holding Option+Command+P+R during startup.
From the Apple KB article:
If you experience issues related to settings stored in NVRAM, resetting NVRAM might help. NVRAM (nonvolatile random-access memory) is a small amount of memory that your Mac uses to store certain settings and access them quickly. Settings that can be stored in NVRAM include sound volume, display resolution, startup-disk selection, time zone, and recent kernel panic information. The settings stored in NVRAM depend on your Mac and the devices you're using with your Mac. If you experience issues related to these settings or others, resetting NVRAM might help. For example, if your Mac starts up from a disk other than the one selected in Startup Disk preferences, or a question mark icon briefly appears before your Mac starts up, you might need to reset NVRAM. Older Mac computers store similar information in PRAM (Parameter RAM) instead of NVRAM. The steps for resetting PRAM are the same as the steps for resetting NVRAM.
Need to create a bootable installer for macOS? It’s a lot easier than it used to be, if you follow Apple’s directions.
- Open Terminal
- Make the script executable by typing: chmod a+x (yourscriptname)
- In Finder, right-click the file
- Select “Open with” and “Other…”
- Here you select the application you want the file to execute into, in this case it would be Terminal.
- To be able to select Terminal, you need to switch from “Recommended Applications” to “All Applications”.
- The Terminal.app application can be found in the Utilities folder
- After clicking OK you should be able to execute the script by simply double-clicking it.