Last updated on May 3rd, 2016 at 09:38 am
I have a 64GB iPhone 5S but my MacBook Air only has a 128GB SSD which is not enough to regularly hold a backup of my phone. iCloud offers 5GB free online space so I have to pick and chose what gets synchronised via iCloud.
I decided to move my iTunes iPhone backup location to a 2GB external drive called Seagate1. This is a really easy process for Mac and Windows users.
There is no way to change that within iTunes. I am sure there must be tools you can get online to configure it but I used the Terminal to create a symbolic link to make iTunes to use the external drive.
By default iTunes stores iPhone backups in ~/Library/Applications Support/MobileSync/Backup on Macs and \AppData\Roaming\Apple Computer\MobileSync\Backup on Windows. If you already have a backup you wish to keep, move the Backup folder to the new backup location on your external drive. Otherwise rename the existing Backup folder to BackupOld.
The symlink links the folder from ~/Library/Application Support/MobileSync/Backup to a backup directory on my external drive – in my case /Volumes/Seagate1/iOSBackups/Backup.
Mac OS X
Open Terminal either by searching for Terminal in spotlight or use Finder to navigate tothe Utilities folder inside your Applications folder.
Terminal will normally open in your home folder with a $ prompt.
Type the following command create the symlink, change Seagate1 to your external drive name.
ln -s /Volumes/Seagate1/iOSBackups/Backup ~/Library/Application\ Support/MobileSync/Backup
That’s it! Connect your iPhone and back it up.
Windows
Open the Command Prompt window by clicking the Start button 
, clicking All Programs, clicking Accessories, and then clicking Command Prompt.
Type the following command to create the symlink ,change SEAGATE1 to your external drive letter.
mklink /J "%APPDATA%\Apple Computer\MobileSync\Backup" "[Your External HDD]:\iOSBackups\Backup"
That’s it! Connect your iPhone and back it up.
