Start up disk full

Hello,

Are you using Filevault?

See if this clears it up:

PRAM RESET

Zap the PRAM

• Shut down the computer.
• Locate the following keys on the keyboard: Command, Option, P, and R. You will need to hold these keys down simultaneously in step 4.
• Turn on the computer.
• Press and hold the Command-Option-P-R keys. You must press this key combination before the gray screen appears.
• Hold the keys down until the computer restarts and you hear the startup sound for the second time.
• Release the keys.

If you are a typical user you probably have large libraries of media, including photographs, music and movies. If that's the case the best thing to do is move each to an external HD. Apple explains how in these articles:

file:///.file/id=7413499.89iMovie: How to move the Library to an EHD

iPhoto: How to move the Library to an EHD

Move an iTunes library from a PC to a Mac (and back)

Obviously the disk is not full. What is the exact, complete text of the warning messages, and what are you doing when you see them?

Have you rebooted since you saw that warning?

Launch the Activity Monitor application. Select the System Memory tab. What values are shown in the bottom part of the window for Page outs and Swap used?

To locate large files, you can use Spotlight. That method may not find large folders that contain a lot of small files.

You can more effectively use a tool such as OmniDiskSweeper (ODS) to explore your volume and find out what's taking up the space. You can also delete files with it, but don't do that unless you're sure that you know what you're deleting and that all data is safely backed up. That means you have multiple backups, not just one.

Deleting files inside an iPhoto or Aperture library will corrupt the library. Any changes to a photo library must be made from within the application that created it. The same goes for Mail files.

Proceed further only if the problem isn't solved by the above steps.

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 see everything, you have to run it as root.

Back up all data now.

Install ODS in the Applications folder as usual. Quit it if it's running.

Triple-click the line of text below on this page to select it, then copy the selected text to the Clipboard (command-C):

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

Launch the Terminal application in either 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.

Paste into the Terminal window (command-V). 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. If you see a message that your username "is not in the sudoers file," then you're not logged in as an administrator.

The application window will open, eventually showing all files in all folders. It may take some minutes for ODS to list all the files.

I don't recommend that you make a habit of doing this. Don't delete anything while running ODS as root. If something needs to be deleted, make sure you know what it is and how it got there, and then delete it by other, safer, means. When in doubt, leave it alone or ask for guidance.

When you're done with ODS, quit it and also quit Terminal.

Have you tried simply just emptying your Trash icon in the OS X dock?

Also, if you use iPhoto, iPhoto has its own trash that needs to be emptied?

Also, make sure you have emptied the Trash in your Apple Mail, too!

Everyone seems to have missed this.

Good work, thanks for the report! 🙂