Mac: Un-mount a Hard Drive using Command Line

Have you ever wanted to un-mount your hard drive from Terminal on your Mac? Probably not. Well guess what? I’m going to show you anyway. I had a hard drive plugged in to my iMac at home and thought it was making my computer crash. I wasn’t at home so I had to SSH in and un-mount it by using command line. I ended up having to use diskutil (disk utility).

Usage: diskutil u[n]mount [force] MountPoint|DiskIdentifier|DeviceNode

I first had to find out the full path name of the drive I wanted to un-mount. You can do this by typing df (disk free).

Example

# df
 Filesystem 512-blocks Used Available Capacity Mounted on
 /dev/disk0s2 487725344 77926824 409286520 16% /
 devfs 218 218 0 100% /dev
 map -hosts 0 0 0 100% /net
 map auto_home 0 0 0 100% /home
 /dev/disk1s2 1951479728 126652704 1824827024 7% /Volumes/Time Machine Backups

I want to un-mount /Volumes/Time Machine Backups.

All I have to do is type diskutil unmount

Example

# diskutil unmount /Volumes/Time\ Machine\ Backups/
 Volume Time Machine Backups on disk1s2 unmounted

As you can see, /Volumes/Time Machine Backups is no longer mounted.

# df
 Filesystem 512-blocks Used Available Capacity Mounted on
 /dev/disk0s2 487725344 77926824 409286520 16% /
 devfs 218 218 0 100% /dev
 map -hosts 0 0 0 100% /net
 map auto_home 0 0 0 100% /home