Remount drive without physically disconnecting?

So I have unmounted a usb external hard drive but I went to re-mount it. Is there a command that I can use to remount the drive? Only way I know to re-mount a drive is to disconnect the usb cable from my Mac and reconnect it.

One-liner:

diskutil mount `diskutil list | grep "Volume Name" | sed -n -e 's/^.* //p'`

1. Find the disk identifier:

   diskutil list | grep "Volume Name"
   

   _{Example result:}

   4:   Apple_HFS Volume Name   100 GB   disk1s2

2. Mount the disk:

   diskutil mount disk1s2
   

Disk Utility will let you remount any connected drives. Just

1. open it up (It is usually in Applications > Utilities)

2. select the drive

3. click "Mount"

diskutil mount also accepts a volume name, so there is no need to grep the output of diskutil list. If the disk has multiple volumes (like a Time Machine volume and another volume), you can use diskutil mountDisk to mount all volumes:

$ diskutil mount WD
Volume WD on WD mounted
$ osascript -e 'tell app "Finder" to disks where ejectable is true'
disk WD
$ diskutil eject Untitled
Disk WD ejected
$ diskutil mountDisk WD
Volume(s) mounted successfully
$ osascript -e 'tell app "Finder" to disks where ejectable is true'
disk Time Machine, disk WD

mountDisk and eject apply to all volumes even if you specify the name of one volume.