A few days ago, I started to have a very disturbing “Not permitted” message when trying to mount a usb disk from Thunar. The only way I found was to pmount the disk : not as intuitive as just clicking the disk on Thunar.
But after some googling, I found where was the real problem : udisk, who is responsible of mounting disks, uses polkit to know if I have the right to mount, or not, external disk. So, if you have the same problem, follow this steps :
sudo nano /usr/share/polkit-1/actions/org.freedesktop.udisks2.policy
(use your favorite text editor in place of nano)
Then, look for the section with “udisks2.filesystem-mount”, inside you’ll have a “defaults” section with interesting stuff :
Now, replace all “auth_admin*” by “yes” to give access for every user, like this :
Save your modifications. Forget this annoying message !