Mounting a drive on macOS is simple; you connect it to a port and it will automatically be mounted. If you want, you can use a Folder Action and have the mounted drive open in Finder when it is mounted. Unmounting is manual since the drive can’t guess when you’re done using it but once you’ve unmounted or ejected a drive, you have to physically disconnect it from a Mac and connect it again if you want to mount it. At least, that’s how most people do it since it’s straight forward but you can mount an ejected drive without physically disconnecting it. The process isn’t the simplest but it is doable.
Mount ejected drive without disconnecting
First, connect the drive to your Mac. Make sure that it is mounted. Once the drive has been mounted, open Terminal and run the command below.
This will list all the drives/disks that are connected to your Mac and it will include the drive you connected. Here, you need to take note of the name of the drive. In the screenshot below, the drive that was mounted is called /dev/disk2. You will notice that this disk has volumes under it. This is fine but when you’re dealing with a disk that has volumes, the command for mounting and unmounting it will differ from if the disk has no volumes. All you need to do is make the distinction and it will be obvious when you run the above command. The numbered items listed under a drive/disk indicate it has volumes.
If the disk has volumes, run the following command to unmount it. Replace the name of the disk with the one your disk has.
diskutil unmountDisk /dev/disk2
If the disk does not have volumes, run the following command to unmount it. Again, change the name of the disk to that of the one you’re unmounting.
diskutil unmount /dev/disk2
Now that the disk has been unmounted, you have to mount it again. The command will differ again based on whether the disk has volumes or not. If the disk has volumes, run the following command. Change the name of the disk accordingly.
diskutil mountDisk /dev/disk2
If the disk does not have volumes, use the command below but change the disk name to the disk you’re mounting.
diskutil mount /dev/disk2
That’s all you need to do. You will no longer have to physically remove a drive and connect it again to your Mac to mount it once it’s been ejected. Removing and reconnecting a drive on a MacBook isn’t too hard but on iMacs, and Mac Minis, the ports aren’t as easy to reach.
You can do this on Windows 10 as well but the process is far more complicated and it has limitations.