My MacBook Air won't shut down when an external hard drive is connected. The screen goes black, and the mouse pointer is still there. I think this started happening when I upgrade to Yosemite. Any suggestions as to how I might fix this?
Are you sure something is not still running...or something is preventing the disk from unmounting.
If there's a grey circle -- then it might be running fsck on the disk...
Now, another thread suggested:
Start Up in Verbose Mode using Command-V
Then issue: sudo shutdown -h now
Also, more /var/log/system.log
This should show you what's occurring as it shuts down.
The sudo shutdown -h now is equivalent to the Shut down menu option.
Also, try going into Disk Utility and manually click on the Unmount icon. I would just want to see if it will unmount normally.
If it doesn't, then, I'm thinking SOMETHING is still using the disk..