To factory reset an old Mac is straightforward with very little prep. Good practice is to ensure the data from the old machine has been copied to the relevant new location. A very simple method to achieve this is to use an ext hard drive and set it up as a Time Machine drive for backups. Other methods like cloud storage either a drag and drop to say dropbox or the built in feature for 365 or Google workspace works fine as long as you have the cloud storage to backup the data.
Tools that can help:
- Good Internet (can you a USB installer of the macOS which removes the internet required)
- Work Bench (for the machine)
- USB Boot Drive (allows you to install which macOS you need)
- keyboard and Mouse (USB for non Laptops)
Steps to factory reset:
Backup the machine
- Backup the machine
- Plug in USB macOS installer
- Boot Machine using the Option Key (Intel Machines)
- Boot Machine (keep power button down for options)
- If your not using a USB Boot macOS installer Cmd R (boots to recover Partition)
- Select your macOS boot method
- Once at the boot menu option, open Disc Utility
- Select Internal drive click Erase (Once done you cannot go back, data is gone)
- Close Disc Utility
- Select macOS to install (Monterey etc)
- Select the internal drive (The one you just formatted)
- Wait for the machine to install macOS
Useful articles.
Mac startup key combinations