Startup Disk full?

[AppleFan22]

Literally two hours ago I had about 150 GB of empty space in my startup disk, now I have (apparently) 9.2 MB. The only things I've done are watch Netflix, browse Facebook, and get Terminal to erase free space. Terminal has finished now, and come up with the error message attached. Any solutions?
[doublepost=1459889997][/doublepost]UPDATE: Immediately after quitting Terminal I gained back the 138 GB that was full. This was confirmed by both Disk Utility and About This Mac. Anyone know WHY this happened in the first place?

 

[Mernak]

Sounds like it could have been a log that Terminal was continually writing to, which caused the disk to fill up. Even if you delete/rm the file, if an running has the file descriptor, the underlying data won't be freed, resulting in still not showing up as free (I've seen something similar happen with an infinite loop in a SQL Developer instance). You can use something lik du -sh (du to show the sizes of all the files in the current dir, -h is human readable [e.g. Using 1KB instead of 1024] and -s is summary [show size of all files under the dir, not just size of the dir link]) to find the offending file, rm it, then lsof (list open file descriptors, might be something ) to find out which process is holding onto the reference and kill that particular process.

 

[Weaselboy]

UPDATE: Immediately after quitting Terminal I gained back the 138 GB that was full. This was confirmed by both Disk Utility and About This Mac. Anyone know WHY this happened in the first place?

When you run that command you did, it creates a large file that fills all the empty space on the disk, then it deletes that large file. It sounds like either the process failed, or you interrupted it before the large file was deleted.

 

[AppleFan22]

When you run that command you did, it creates a large file that fills all the empty space on the disk, then it deletes that large file. It sounds like either the process failed, or you interrupted it before the large file was deleted.

The same thing happened again the other day, however the computer was left alone to do its business overnight. However, when I turned the display back on in the morning, there were two notifications, one from Photos, saying my full-res photos could not be downloaded from iCloud (yet I have "Download and store originals on this Mac" turned on), and one from App Store, redgarding a failed software update. I'll try again tonight to do it, but disconnecting the Mac from all internet activity.