14.04.5 LTS.

I need Firefox >=48 for my Travis build: https://travis-ci.org/umts/incidents/builds/240872628

So I sudo apt-get update and sudo apt-get install firefox, which says:

Unpacking firefox (53.0.3+build1-0ubuntu0.14.04.2) ...


But then my automated tests were failing with the same exact message as when I had the built-in version of firefox (38.4.0esr). So as a sanity check, I added firefox -v after the install, which returns:

(process:5877): GLib-CRITICAL **: g_slice_set_config: assertion 'sys_page_size == 0' failed
Mozilla Firefox 38.4.0

Perhaps that failed C assertion is meaningful here? But on the face of it, apt is installing one version of a package, but then using that package gives me a much older version, despite apt having returned no error messages.

How can I successfully install and use Firefox >=48 in this context?

  • What is the output of whereis firefox | tr ' ' '\n' | grep bin?
    – Ravexina
    Jun 8, 2017 at 17:20
  • /usr/bin/firefox /usr/bin/X11/firefox /usr/local/bin/firefox
    – dfaulken
    Jun 8, 2017 at 17:24
  • the out put of which firefox and dpkg -S $(which firefox)
    – Ravexina
    Jun 8, 2017 at 17:25
  • which firefox /usr/local/bin/firefox dpkg -S $(which firefox) dpkg-query: no path found matching pattern /usr/local/bin/firefox
    – dfaulken
    Jun 8, 2017 at 17:36

2 Answers 2


On Travis CI, Firefox is pre-installed at /usr/bin/X11/firefox, which seems to be the build geckodriver was using, regardless of whether I used update-alternatives to specify which one I wanted.

So I started my build with:

whereis firefox | tr ' ' '\n' | grep bin | xargs sudo rm

to remove all existing versions of firefox. Then sudo apt-get update and sudo apt-get install firefox as in my question. This worked.

Thanks Ravexina for your debugging help!


Seems you have two version of Firefox installed on your Ubuntu.

one which has been installed using package manager is located at:


the other which your system is using (I guess you installed it somehow manually) is located at:



sudo update-alternatives --config x-www-browser

to set the /usr/bin/firefox as your default browser. you can also run it using absolute path like /usr/bin/firefox, for example to see the version of firefox:

/usr/bin/firefox -v
  • As I mentioned, this is an automated Travis build, so I'd want sudo update-alternatives --set x-www-browser /usr/bin/firefox to avoid interactive mode. I'll give it a try.
    – dfaulken
    Jun 8, 2017 at 18:24
  • I ended up fixing it by piping one of your debugging commands: whereis firefox | tr ' ' '\n' | grep bin to xargs sudo rm before installing the correct Firefox. This did it.
    – dfaulken
    Jun 8, 2017 at 18:38
  • It wasn't a good thing to do ;)
    – Ravexina
    Jun 8, 2017 at 18:58
  • If you have a better solution than removing existing versions of Firefox, I'm certainly happy to accept them.
    – dfaulken
    Jun 10, 2017 at 3:53

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