After having upgraded to OS X Yosemite, a number of people have found their Macs now take a relatively long time to log in. While powering on the system will reveal the login screen almost immediately, after supplying an account password the system will show a progress bar and hang for up to a couple of minutes, before finally showing the desktop and allowing the computer to be used.
If this is happening to you, then the problem is very likely from a bug with how Yosemite is handling your FileVault disk encryption that you set up prior to upgrading to Yosemite.
FileVault 2 is Apple’s full-disk encryption routine that will encrypt all files on your hard disk, including the OS. When set up, the OS will not load when you start up your system, and the login window you see is just a pretty interface that mimics the login window, and allows you to supply a password for accounts that are able to unlock the disk.
If you are noticing this problem with your Mac after upgrading to Yosemite, then you can likely fix the problem by turning FileVault off and then back on again:
- Ensure you have a full backup of your Mac using Time Machine.
- Boot and unlock your Mac as you normally would to log in.
- Go to the FileVault tab in the Security & Privacy system preferences and turn off FileVault.
- When FileVault is disabled and your drive is decrypted, restart your Mac.
- Hold the Command-R keys down at the boot chimes to load your Mac into Recovery Mode.
- Open Disk Utility and use it to run a Repair Disk routine, available in the First Aid tab when you select your hard drive. Do this for both the hard drive device, and your boot volume.
- Restart your Mac normally and log in.
- Re-enable FileVault in the Security & Privacy system preferences.
The above routine works for if you can eventually boot your Mac in the face of this bug, but if you cannot log in and see the system hang on the loading progress bar for hours with no ability to use your system, then you will have to use another procedure:
- Reboot your system and hold the Command-R keys at the startup chimes to load into Recovery Mode.
- Use Disk Utility to turn off encryption on your boot drive. If this gives you errors, then reboot in Target Disk Mode (hold the T key at the boot chimes) and use Disk Utility on another Mac via a Thunderbolt or Firewire cable to turn off encryption. Alternatively, you can try booting to Internet Recovery by holding Option-Command-R at the boot chimes, which will avoid using your internal drive for any boot purposes.
- With your drive unlocked and decrypted, use Disk Utility to verify and repair your boot drive.
- Restart your Mac normally.
- Use the Security & Privacy system preferences to re-enable FileVault.