In 2012 I used Ubuntu's gnome-disks utility to encrypt an external drive.
Last year I was still being able to unlock it.

But today I tried again on Ubuntu 2012.04 and gnome-disks says:

Error unlocking encrypted device
Not authorized to perform operation (udisks-error-quark, 4)

How to solve this and unlock my data?

Not authorized to perform operation (udisks-error-quark, 4)


The error code 4 returned by udisks2 (which is used by gnome-disks-utilities internally) is the constant UDISKS_ERROR_NOT_AUTHORIZED_CAN_OBTAIN in code.

This code is returned, if the current subject (the gnome-disks applications, actually) is not allowed to do the unlock operation, however it might be allowed if further authentication would be provided, typically by providing the system administrator's (root) password.

Such additional password query is typically handled by a so-called authentication agent. It seems that this agent is not setup correctly in your environment.

I had the same problem using gnome-disks within an i3wm-session (in archlinux -- however this should be similar under Ubuntu): After having installed the (legacy) "polkit-gnome" authentication agent (and starting it in a session startup script), I got first the passphrase dialog for specifying the LUKS passphrase of the device and then a second dialog asking for the root password.

The command line hack you mention can alternatively also be done using udisksctl in an cleaner way:

udisksctl unlock --block-device /dev/sda1
udisksctl mount --block-device /dev/mapper/my_encrypted_volume

Note that the udisksctl unlock will ask for the (same) two passwords as gnome-disks would do when the authentication agent is setup correctly. No need to use sudo here.

For further information, dig into udisks2 and polkit documentation or look into udisks2 source code directly. This is how I understood and finally solved the problem for me.

  • Error unlocking /dev/sda1: GDBus.Error:org.freedesktop.UDisks2.Error.Failed: Error unlocking /dev/sda1: Failed to activate device: Operation not permitted – Mehdi Aug 15 '19 at 12:43

The problem can be solved with sudo:

gksudo gnome-disks

then, operate normaly

  • This worked for me. – Hitesh Sahu Oct 26 '18 at 11:32
  • Why do we have to use sudo now but didnt before? This just started happening to me! – Gabriel Staples Dec 15 '19 at 2:09
  • Ubuntu 18 removed gksudo, so I just used sudo gnome-disks instead. There seemed to be a big delay (~5 seconds) between clicking the button to unlock the partition and the dialog popping up for me to type the password in, but otherwise it worked just fine. – Gabriel Staples Dec 15 '19 at 2:19

What helped me is very similar to Thrushbeard’s explanation, but I can’t post comments yet.

I installed mate-polkit and then executed /usr/lib/x86_64-linux-gnu/polkit-mate-authentication-agent-1. If you’re not using Mate, then there’s an overview over all the Polkit packages. Click the respective link on that wiki page and then “View the file list for [package]” to find the name of the executable for your environment. I hope it helps!


The problem can be solved via command line:

sudo cryptsetup luksOpen /dev/sda1 my_encrypted_volume
sudo mkdir /media/adhoc
sudo mount /dev/mapper/my_encrypted_volume /media/adhoc

You can now access your files in the /media/adhoc folder.
my_encrypted_volume and adhoc can be whatever name you want (no space), anything will work.

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