IPhone – Message: not enough computer space for iphone backup

When you start syncing your iDevice in iTunes and then you get this annoying message (especially when it tells you it needs like 1.4MB and there is 300MB available?!): 'The iPhone/iPad “iPhone(insert name)” cannot be synced because there is not enough free space to hold all the selected items'. What do you do?

Basically the problem, in many cases, seems to be that iTunes thinks it has too many updates to install on your iPhone/iPad and it isn't smart enough to load them one at a time when there's not enough space to do them all??

Fortunately it can often be side-stepped by just taking your iPhone/iPad and clicking on the App Store app, then tapping on the Updates tab, and then tapping on 'Update All' at the top right. If that complains that there's not enough space you can let do some updates then try again (and again) and will update the rest of the apps. Then the sync should be fine with iTunes.

I've run into this before when using networked backup, also said something like 497GiB were free when actually 4TiB were free. Seems this is caused by TM not creating a large enough sparsebundle for the initial backup. I found a workaround that at least worked for me (El Capitan) and submitted a bug report to Apple.

Workaround: You should notice that the sparsebundle on the OS X server has only ~499GiB as its capacity. Manually enlarge it by running this command on the server: sudo hdiutil resize -size [number of gigabytes]g [path to sparsebundle], e.g. sudo hdiutil resize -size 10000g /Volumes/Backups/mybackup.sparsebundle. Make it as large as you need. Retry your backup.

Edit: You may also have to resize the sparsebundle's partition in Disk Utility. I didn't have to do this, but maybe that's because my backup wasn't encrypted. For instructions, see the first (not accepted) answer here: Increase size of sparsebundle for TimeMachine