`fusermount3: mount failed: Permission denied`

[vitaly-zdanevich]

Also I see Nvidia driver handler disabled due to unionfs errors.

I tried ./conty steam.

Ubuntu 25.04

[Kron4ek]

You can work around that by disabling AppArmor.

https://bugs.launchpad.net/ubuntu/+source/fuse3/+bug/2111105

[vitaly-zdanevich]

What is the root cause?

[Kron4ek]

I don't know, it seems AppArmor is restricting FUSE in Ubuntu 25.04, which wasn't the case in older Ubuntu versions. In any case, it's likely a bug that will be fixed in future Ubuntu updates.

[Kron4ek]

I just tried Conty on a clean Ubuntu 25.04 in a virtual machine, it works fine mostly, but unionfs-fuse (and thus the Nvidia driver handler) doesn't work until you disable AppArmor and reboot your system.

# systemctl disable apparmor