Two options are to use Duplicate (a free utility which can copy and paste an entire bootable volume), or Mac Backup Guru (a paid, fully featured backup utility with unique incremental backups capability) for that.

Backup all the data to an external disk with a clone.Download the macOS installer from Apple.Here is the clean install procedure which can be performed at least every time a new version of macOS is released: However, it has been shown in recent times that in the vast majority of cases if you simply run a clean install, then duplicate your old home folder to your new disk, you will get all of the same advantages as a clean install followed by manual migration, with a small fraction of the effort. It used to be common practice to occasionally run a clean install, and then manually migrate all the files and settings over in order to get a completely fresh start. That will make your Mac run blazingly fast for a few months or more, and many people report that it fixes longstanding problems they’ve had too. When you install a new major version of OS X, or after some time has passed, it is a good idea to do a clean install (that is, to erase the disk you are installing OS X onto as part of the installation process).

Create mac os usb for another mac