I use okular for annotating some of my PDFs but have been having an issue recently where I can only open files that are on my SSD where I installed ubuntu, but not on the 2nd hard drive (located at /mnt/...).

When run from terminal the output I get is:

Qt: Session management error: None of the authentication protocols specified are supported
org.kde.knotifications: Audio notification requested, but sound file from notifyrc file was not found, aborting audio notification

When doing the same to the file on the SSD I get the first message (though not the second, but I think that is just it wanting to use sound to warn me that it couldn't open the file). I have also run it under sudo just incase it was a permission error and get

[error] cannot open locale definition file `en': No such file or directory
No protocol specified
qt.qpa.xcb: could not connect to display :1
qt.qpa.plugin: Could not load the Qt platform plugin "xcb" in "" even though it was found.
This application failed to start because no Qt platform plugin could be initialized. Reinstalling the application may fix this problem.

I have also tried with other programs and don't see this distinction (including being able to open the same file on the 2nd HDD in a different program).

  • Did you install okular as a snap? May 4, 2020 at 13:52
  • Had a look and yes I had, I can kind of imagine how that would be related, but is there a known issue? May 5, 2020 at 6:18

1 Answer 1


Snaps can only access certain files in your filesystem. Depending on how it was created, usually that includes the user's home and its subfolders. Some snaps include a plugin to also access removable media (hardcoded as /media).

That is the current security model of snaps, they have to declare what they intend to access.

Fixes: You could try to install with --classic to recreate the snap from source, modifying the snapcraft.yml to change the containment. You still need snapd to play along and allow it.

As a general note, snaps should not be regarded as drop-in substitutes for system packages for exactly this reason. VLC snaps for example will not allow you to play media from an arbitrary folder (even if you have the rights to do so).

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