Recover erased free disk

Use a tool such as OmniDiskSweeper to explore your volume and find out what's taking up the space.

Proceed further only if the problem hasn't been solved.

ODS can't see the whole filesystem when you run it just by double-clicking; it only sees files that you have permission to read. To really see everything, you have to run it as root.

First, back up all data if you haven't already done so. No matter what happens, you should be able to restore your system to the state it was in at the time of that backup.

Launch the Terminal application in any of the following ways:

☞ Enter the first few letters of its name into a Spotlight search. Select it in the results (it should be at the top.)

☞ In the Finder, select Go ▹ Utilities from the menu bar, or press the key combination shift-command-U. The application is in the folder that opens.

☞ If you’re running Mac OS X 10.7 or later, open LaunchPad. Click Utilities, then Terminal in the page that opens.

Drag or copy – do not type – the following line into the Terminal window, then press return:

sudo /Applications/OmniDiskSweeper.app/Contents/MacOS/OmniDiskSweeper

You'll be prompted for your login password, which won't be displayed when you type it. You may get a one-time warning not to screw up.

I don't recommend that you make a habit of this. Don't delete anything while running ODS as root. When you're done with it, quit it and also quit Terminal.

You're seeing everything on the volume. There is nothing else. If you're not convinced, erase and restore from backup.

my Macintosh HD shows less (at OmniDiskSweeper Drive List) 30gb (in total) than it was supposed to. It shows 370gb when it should be 399gb. Although the values are normal when I check them at Finder (Macintosh HD icon info).

It sounds as if you are referring to the total capacity of the volume. If free space were being taken up by hidden items, it should not affect that value,

If you are referring to an apparent 30GB discrepancy in total capacity between OmniDiskSweeper's Drive List report and Finder's Get Info report, that does not represent a true difference. That discrepancy is about 7% of the total, and in my system all of the disk space parameters - total capacity, used space, and available (free) space are reported about 7% smaller in OmniDiskSweeper's Drive List window as compared Finder's Get Info window:

.

.

The reason for this is presumably that the GB units are different! OS X changed to a smaller "decimal" unit of measurement as of Snow Leopard, and a decimal GB (gigabyte) is about 7% smaller than the binary GB used previously, and which apparently is still being used by OmniDiskSweeper. The binary unit is more properly called GiB (gibibyte) to tell it apart.

For my "Lacie Lion 2" boot disk above, the Terminal command

df -H /

gives "gigabytes"

-----------------

Filesystem Size Used Avail Capacity Mounted on

/dev/disk1s3 159G 110G 49G 70% /

---------------------

which is as reported in Get Info

whereas the Terminal command

df -h /

gives "gibibytes"

-------------------

Filesystem Size Used Avail Capacity Mounted on

/dev/disk1s3 148Gi 102Gi 45Gi 70% /

--------------------

which is as reported by OmniDiskSweeper

I got the same OCCCrashCatcher message, but then when I clicked on OmniDiskSweekper it found 493GB of files as opposed to the 190GB it was finding before

Thanks 🙂

PS What on earth does the OCCCCrashCatcher message mean?