Xfce Forum

xfce_user16

Member

Registered: 2025-07-16

Posts: 2

Failed to execute default Web Browser. Input/output error.

I want to preface this that I really have no idea if this is an XFCE4, Ubuntu, Snap, Firefox, or some other application's problem. The error message is terrible and there is near zero information in logs.

I have no idea where to go from here. Some questions that I have:

- How can I get a better error message?
- How can I get better logging for debugging?
- What other logs or such should I be checking?
- Where should I be opening a bug report (or reports)?

# Problem Description

Over the last couple of weeks as my systems have been updating, the ability to open the system web browser has broken. It was previously working. I can manually open Firefox from the terminal (firefox) or if I use exo-open --launch WebBrowser. However, attempts to open Firefox using the web browser icons from any panel, the Firefox application icon, or any attempt by other applications to launch the web browser fail.

The error message provides no useful information, "Failed to execute default Web Browser. Input/output error."

From the user's .xsession-errors file:


cannot set memlock limit to 524288:524288: Operation not permitted


From system logs:


Jul 16 23:59:27 affecthost systemd[1919]: Started snap.firefox.firefox-d9004373-337f-4dac-b715-79bc8f8d3dda.scope.
░░ Subject: A start job for unit UNIT has finished successfully
░░ Defined-By: systemd
░░ Support: http://www.ubuntu.com/support
░░
░░ A start job for unit UNIT has finished successfully.
░░
░░ The job identifier is 496.


# System Info

OS: Ubuntu 22.04.5 LTS (server, not desktop)
Xfce: 4.16
Firefox: 140.0.4

# Things That I Have Tried

- Resetting the default web browser through the UI and through manually editing the conf file. No change.
- Installing a different browser, Chromium. No change.
- Restarting the system. No change. Also, this is affecting multiple systems now.
- Starting Firefox from terminal. This works, but doesn't scale for other users.

Last edited by xfce_user16 (2025-07-17 00:16:51)

eriefisher

Wanderer

From: ON, Canada

Registered: 2008-10-25

Posts: 753

Re: Failed to execute default Web Browser. Input/output error.

Why are you using a snap for Firefox? Why are you running a server release with an old graphical environment?

---

I AM CANADIAN!
Siduction
Debian Sid
Xfce 4.20 with Wayland/Labwc

kism

Member

Registered: 2025-07-21

Posts: 1

Re: Failed to execute default Web Browser. Input/output error.

Hello, I have got the issue on all my Ubuntu 20.04/22.04 VMs running XFCE. It seems to be something wrong with the apparmor config for the snap packages.

So far my only workaround is installing firefox-esr from the mozilla ppa (its a .deb not a snap), Or installing google chrome (.deb). No issues on 24.04. If you run firefox via the commandline, on a system that hasn't had the issue yet the text "Regenerate security profiles" comes up first.

If you run it from the terminal with strace enabled, it weirdly works.

snap run --strace firefox

Last edited by kism (2025-07-21 06:39:16)

xfce_user16

Member

Registered: 2025-07-16

Posts: 2

Re: Failed to execute default Web Browser. Input/output error.

Why are you using a snap for Firefox? Why are you running a server release with an old graphical environment?

Do you have any suggestions on how to troubleshoot this issue? To keep system configuration and management as simple as possible, our builds use system/distro default packages and repos.

1. Why are you using a snap for Firefox?

It is the default installation target for Ubuntu.

2. Why are you running a server release with an old graphical environment?

It is the default installation target for Ubuntu.

Added later 03 min 10 s:

Hello, I have got the issue on all my Ubuntu 20.04/22.04 VMs running XFCE. It seems to be something wrong with the apparmor config for the snap packages.

So far my only workaround is installing firefox-esr from the mozilla ppa (its a .deb not a snap), Or installing google chrome (.deb). No issues on 24.04. If you run firefox via the commandline, on a system that hasn't had the issue yet the text "Regenerate security profiles" comes up first.

If you run it from the terminal with strace enabled, it weirdly works.

snap run --strace firefox

I'll test the upstream Firefox package installation. As I mentioned in the previous post, we do prefer to use distro defaults where possible but we do make exceptions when they lack the software or (in this case) the default is broken.

Also, as mentioned, Firefox runs if I simply execute `firefox` from the terminal, no need to use snap and such.

Added later 06 min 26 s:

Why are you using a snap for Firefox? Why are you running a server release with an old graphical environment?

Also, if you have suggestions on a better place to ask this question, please let me know. As mentioned in the OP, I have almost zero log information to go from so it is not clear to me where the bug or misconfiguration lies. I'm starting here because the problem seems to be with Xfce desktop environment and the default web browser application.

Last edited by xfce_user16 (2025-08-16 01:05:40)