Ubuntu – Disk Utility: What’s the difference between “Unmount” and “Safe Removal”

10.10disksoftware-recommendationudisksumount

System > Administration > Disk Utility

What's the difference between "Unmount Volume" and "Safe Removal"? Say you insert a flash drive and open the Disk Utility UI, if you click on "Safe Removal" you receive an "Error Detaching Drive" notification, because it's busy. You must first click the "Unmount Volume" button, and then follow it with the "Safe Removal" button.

A couple questions here: Does this mean all these times I've been "ejecting" the drive (via context menu) before removing it, I haven't been "safely" removing it? And what are the command line equivalents for the two different operations?

(This question was somewhat addressed here but the answers seem to contradict what I'm pointing out about the Disk Utility options. Thanks.)

Best Answer

"Unmount" unmounts a filesystem. If your USB mass storage device (e.g. USB memory sticks or USB hard disks) contains more than one partition, this will only unmount the filesystem on the currently selected partition.

"Safe removal" does the same as "eject" I suppose. In case of USB mass storage devices it powers down the device, which makes it inaccessible (it will disappear from the device list until you unplug & plug it in again). Powering down the device before unmounting would have the same result as disconnecting the usb device without unmounting: possible data loss.

From a usability point of view, it would be better if clicking the "safe removal" button for a device that still has mounted filesystems on it would just ask if it's okay to unmount those filesystems, or maybe even just do that without asking, because that's most likely what the user wants...

The commandline-equivalents of the Disk Utility buttons are:

udisks --unmount for the "Unmount" button
udisks --detach for the "Safe Removal" button

Related Solutions

Root Privileges for Umount – How to Change Command Line Permissions

Nautilus doesn't unmount the device directly; it talks over DBus to a system daemon (udisks-daemon) and asks it to unmount.

The daemon checks if you're allowed to do that, by contacting another system daemon, PolicyKit.

PolicyKit uses the configuration defined in /usr/share/polkit-1/actions/org.freedesktop.udisks.policy (unless the local system administrator overrides it in /etc/polkit-1). That file tells PolicyKit that users with active console sessions can detatch drives, so PolicyKit talks to a third daemon, ConsoleKit, to see if you have active console sessions. Logging in via gdm counts as a console session; logging in via ssh doesn't.

There's a command-line tool udisks that lets you unmount devices without using sudo, using the same mechanism:

udisks --unmount /dev/sdb1

that unmounts the filesystem; I can also detatch the whole device with

udisks --detach /dev/sdb

which makes the LED on my USB key go dark.

Ubuntu – How to open the Disk Utility in Unity

Accessing Disk Utility:

I'm sorry you have encountered this level of confusion. Help is referring to the activities overlay that is in GNOME Shell, but you are most likely using Ubuntu's Unity Desktop. Since both are "Shells" for GNOME, the help can overlap sometimes.

What you need to do is open the Unity Dash (it's the button with the Ubuntu logo on the upper left), and type Disk Utility.

Dash the rabbit...

Gparted:

However, as Bruno pointed out, you need to install Gparted to actually create partitions with a GUI.

To do this, open the Software Center, search for Gparted, and click install. (Or click this icon: gparted )