I'm trying to make Firefox launch Transmission whenever I click a magnet link. I followed the instructions in https://support.mozilla.org/en-US/questions/1012864 and I successfully managed to get the 'Launch Application' window when I click a magnet link. However, when I try to navigate down to the Transmission directory to select it (which in my case is found in /usr/bin/transmission-gtk), Firefox throws an error just right after I try to access /usr. The error reads "Could not read the contents of usr. Error opening directory /usr: permission denied". Here is a screen capture showing the error:

Permissions Error

I'm not an expert on permissions, but apparently /usr/ is owned by root and everyone else has read permissions; this is what a ls -l / returns:

drwxr-xr-x  12 root root       4096 ago 15 23:23 usr

The Firefox processes are also owned by me (hulahop is my user name), according to ps aux:

hulahop  23113  8.1  4.1 3456980 684420 tty2   Sl+  ago15   2:18 /snap/firefox/243/firefox

There are other child processes but their owner is the same user. How could I get Firefox to forward magnet links to Transmission? I'm running Firefox 68.0.1 (64-bit) on Ubuntu 18.04 LTS. Firefox was installed directly from the Software Center and its permissions are set as follows

Software Center permissions for Firefox

Another issue I'm having with Firefox, which I suspect could be related to the previous one, is that Webgl pages do not work anymore. I have force-enabled webgl within the about:config page (as indicated in https://www.sitepoint.com/firefox-enable-webgl-blacklisted-graphics-card/), but still nothing. I'm sure it's not a problem related to my graphics card or its drivers since webgl-powered pages run perfectly smooth on Chromium, which is also installed in this computer.

The fun thing is that Firefox used to work fine until (I think) the certificate expiration shenanigans that killed all add-ons a few months ago. Before this, I could use the 3D satellite view of Google Maps with no problems (which requires webgl) and handle magnets all right with Transmission. But when that certificate expired, I had to replace Firefox with the Nightly version for a few days, then come back to the stable version, and a few weeks afterwards I started to notice all these issues...

Does anyone have any ideas? Any help will be very much appreciated.

Thanks and best regards, P.

PS: Another fun thing - I've just discovered that I cannot really change the permissions defined for Firefox in the Software Center. Whenever I flick any of the switches I'm asked for the root password, and afterwards I can switch all the options as I want. But when I close the window and reopen it again, I don't see any of the changes I made... My Ubuntu is terribly broken isn't it?

  • 2
    Snap programs are run in a sandbox; the default configs are blocking access to /usr. Can you install the regular version (from the repos) of Firefox and see if it works better? Aug 15, 2019 at 23:20
  • Installing Firefox by means of {sudo apt install firefox}, as proposed by ajgringo619, did fix all the issues: I can access /usr and run webgl smoothly. What still puzzles me is that Chromium was also installed with the aid of the Software Center and works flawlessly with no further intervention. Firefox does not. It would be nice to know how to configure its permissions.
    – TheHop
    Aug 16, 2019 at 15:40

1 Answer 1


The suggestion made by ajgringo619 in its comment did fix all the issues with permissions (I can now access /usr/bin and run webgl pages). The idea is to install firefox by means of sudo apt install firefox instead of with Ubuntu's Software Center. It's a viable work around, although it would be nice to be able to manage all applications from the same point (i.e. the Software Center).

Another interesting point is that Chromium was installed from the Software Center and runs smoothly, Firefox does not. There must be a proper way to configure permissions for Firefox when installed as a Snap program.

In any case, thanks for your suggestion ajgringo619.

  • "There must be a proper way to configure permissions for Firefox when installed as a Snap program." Doubt it. Sandboxed means exactly what it says: for this to work you would need a "firefox+transmission" snap. It would then start transmission in the sandboxed firefox (the download will then also happen IN the snap's Downloads dir).
    – Rinzwind
    Aug 16, 2019 at 15:59

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