512gb iPhone 11 Pro too big to backup

Because my iPhone would completely eat up all of my storage, I am desperately trying to find a way to backup and access my iPhone from an external drive. This is EXTREMELY frustrating! I do NOT use iCloud backup. I prefer to backup directly to a hard device I own.

The solution is to create a symbolic link to the backup location.

ln -s <desired location> <existing location>

where

<desired location> is the fully qualified pathname to your desired backup location

<existing location> is the Finder's default, probably ~/Library/Application Support/MobileSync/Backup/

FWIW, not everything on the iPhone is "backed up".

The only items that are backed up is actual application

data/preferences, not the apps themselves, and a database of

of music, movies, pod casts, etc. so that they can be

re-downloaded when a device restore is necessary.

Example, my iPhone 11 Pro has 45 GB used, but my "backup" is only

900 MB (0.9 GB).

It is often a common misconception that the entire iDevice contents

is copied to your Mac when backed up.

John Galt provided the answer. Here is a more detailed basic step by step description with illustrations for creating a symbolic link to change the iPhone backup location from your Mac to an external hard drive:

https://www.iclarified.com/72786/how-to-change-your-iphone-backup-location-mac

But from a security and reliability point of view, iCloud Backup is a better choice.