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I found a way to put your iPhone backups on the external drive, but how do you find the Library folder to get to the Application Support?

Mac OS X

The original location of the Backups is in a folder called MobileSync

This folder is located in: ~/Library/Application Support

And to do move this folder's location, you will have to:

Copy the folder to the new location (for example at the root of an external hard disk drive (HDD)
Go to ~/Library/Application Support/MobileSync/
Remove the folder "Backup" within or rename it "BackupOld" if you want to keep it
Open Terminal
Type the following command:

ln -s /Volumes/<Your External HDD>/MobileSync/Backup ~/Library/Application\ Support/MobileSync/Backup

Close Terminal
Launch a backup, see if it has been properly located and iTunes sees is as the latest

Voilà, saving precious disk space on Mac OS is easy!

http://support.digidna.net/hc/en-us...-your-iPhone-Backups-on-an-Alternate-Location
 
In Finder, click "Go" in the menu bar and press the "Option" key. "Library" will show up in the drop down list and you're on your way.
 
Will this also work on WiFi (My Cloud) external drive?
Is the name of the external drive same as the one that appears on the left pane on the Finder?
 
On my iMac I just back up Time Machine to the external HD and all are there. That's all I use the HD for.
 
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256gb may fill up quick. I think mine is 1tb. Not sure as my son gave it to me. iMac does delete old ones though as drive fills up. I don't remember size of first back up.
 
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