On my Devuan GNU/Linux system, I have a newer version of Firefox installed, under `/opt/firefox` . I also have /usr/local/bin/firefox point to it, indirectly, via Debian's `alternatives` mechanism (i.e. via `/etc/alternatives/firefox`).

When I just start firefox and it's not already running - this works fine. But if it *is* already running, then startup takes a long time, and eventually I get that dreaded error message box:

> 
> Firefox is already running, but is not responding. To use Firefox, you must first close the existing Firefox process, restart your device, or use a different profile.
> 
> 
> 

Now, I don't have `_MOZ_NO_REMOTE` set; and I don't start firefox with a `-no-remote` option.

What can I do to prevent the above error (and thus allow opening links with a `firefox https://foo.bar/` command)?

Notes:

* Obviously, I don't want to close the existing running instance.
* Not a dupe of [this](https://superuser.com/questions/1359648/firefox-is-already-running-but-is-not-responding-even-though-moz-no-remote-0), which has MOZ\_NO\_REMOTE set to 0.
* Not a dupe of [this](https://superuser.com/questions/851760/firefox-is-already-running-but-not-responding), which involves specific Thunderbird-Firefox interaction.
* Not a dupe of [this](https://superuser.com/q/78917/122798), as I don't seem to have any `parent.lock` file anywhere.