I am having a problem with Firefox not resuming in a new session as sandboxed, when it had that status as the session was saved

In Session Management - System Settings -> Restore manually saved session, I'd like to know how to make Firefox restart under the control of Firejail. Firejail is in the LinuxMint repo, and probably in others, as well.

Before troubleshooting, set KDE Session Manager to "Restore manually saved session".

How to reproduce the problem:

Start synaptic
Install firejail
Install firetools
Open firetools, double-click on Firefox icon
Firefox loads and runs
Right-click on firetools window, select Tools
Window opens, "Firejail Tools and Stats"
In Sandbox List, note firefox is running in firejail

In Kickoff Application Manager, select Leave -> Save session

Log off/reboot to terminate session. KDE then restores session.
Firefox loads and runs, however it is now running outside of the sandbox.

I want to make Firefox resume inside the sandbox. To make it easier, I wouldn't mind to always resume inside the sandbox, regardless of its status when the session was saved.

I've tried placing a symlink into /usr/local/bin as described here, but then there were problems with Firefox finding its Profile.

Could someone please let me know how it's possible to make, or force, Firefox to always restart in the Firejail sandbox?

Firejail v0.9.30-1

The clients are required to tell the SM the command to use to restart them.
It seems firejail is a wrapper to call the firefox binary, but firefox (the actual process) doesn't know that and simply asks to restart firefox.

You could edit ~/.config/ksmserverrc to alter the restart command for firefox after saving the session.
If the path isn't absolute (ie, "firefox", not "/usr/bin/firefox") you could try to shadow the binary by something higher up in $PATH (often /usr/local/bin or ~/bin) with a bash script

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#!/bin/sh
/usr/bin/firejail /usr/bin/firefox


ensure to make it executable

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cmod +x /usr/local/bin/firefox

I have created the script and made it executable.

Now, when I run Firefox from the program launcher menu (Kickoff) I get this error message -- and then, the program's execution aborts:

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Profile Missing
[!] Your Firefox profile cannot be loaded. It may be missing or inaccessible.

The same thing happens when I start it by executing the script.
When I click on the Firefox icon, in Firejail Tools, the browser runs normally, after showing a box asking that it be "made the default browser".

Can anyone duplicate this problem of Firefox losing its profile when started in this manner, and what's the most likely cure?

Second problem:
After (what I thought was) an aborted launch when using the script -- the one with the path pre-pended to 'firejail' and 'firefox' -- and then looking at the Firejail Tools and Stats window , I see this:

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Sandbox List
PID    CPU(%)   Memory(KiB)      RX(KB/s)      TX(KB/s)        Command
10868  0.00        96028             0.00          0.00       /usr/bin/firejail /usr/bin/firefox
10975  5.20        548480            0.00          0.00       firejail firefox

Firefox appears to be running in duplicate, but still there's only one entry on the Task Bar.

Is anyone able to duplicate this behavior, seen when starting Firefox with the script, and any idea what to do about it?