Free disk space in Finder vs Terminal df command

df is basing its calculations on disk blocks and reporting them in bytes. That is actually 68.16 GB. The Finder is looking at file sizes. They are both correct, depending on the context.

See

OS X Lion: About Time Machine's "local snapshots" on portable Macs

which includes the following:

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Note: You may notice a difference in available space statistics between Disk Utility, Finder, and Get Info inspectors. This is expected and can be safely ignored. The Finder displays the available space on the disk without accounting for the local snapshots, because local snapshots will surrender their disk space if needed.

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Go to the "About this Mac" section in the Apple menu, then choose "More Info" and then click "Storage." In here you will see a purple/pink section called "Backups" that should be the size of the difference between the Finder's reported disk availability and that of Disk Utility, df, and other utilities.

tuscan wrote:

do i get your answer right:

this means the Finder is reporting an amount of free space one can never use?

its number includes those bytes that are unused in used disk blocks?

e.g. say a block is 8k an my specific disk, and i'm saving a file with 1k of text.

the Finder would report 7k of these 8k as free space?

while df takes the whole 8k block as "used"?

As jsd2 points out, it is more complicated than that. I don't have local snapshots running on my machine but I still have a significant discrepancy, although not as large as yours.

df is a fast tool and only looks at blocks. The Finder does more work and keeps track of file sizes and, apparently, the potential to delete them. But if you had a one-byte file, those other 4095 bytes wouldn't necessarily be wasted. You could write another 4095 bytes to that file without losing any disk space.

Here's a blog post explaining where the backups referred to in that Backups segment are stored, and how to remove them:

http://blog.valerio.de/post/19238158977/hidden-local-backups-with-mac-os-x-lion- filling-up-your