fusermount: too many FUSE filesystems mounted error

[krillin666]

The following error has been preventing me from launching any AppImage file I have:

fusermount: too many FUSE filesystems mounted; mount_max=N can be set in /etc/fuse.conf

Cannot mount AppImage, please check your FUSE setup.
You might still be able to extract the contents of this AppImage 
if you run it with the --appimage-extract option. 
See https://github.com/AppImage/AppImageKit/wiki/FUSE 
for more information
open dir error: No such file or directory

I'm running Fedora 36. The only other relevant information I can give is that until 2 days ago I was using Xorg and now switched to Wayland.

Thank you for your time !

[probonopd]

When this happens, what is the output of mount, do you see many fuse mounted mountpoints there?

[BobSynfig]

fusermount: too many FUSE filesystems mounted; mount_max=N can be set in /etc/fuse.conf

And applying this advice isn't working?

[probonopd]

@BobSynfig when this happens, what is the output of mount, do you see many fuse mounted mountpoints there?

[BobSynfig]

I doubt that AppimageKit is responsible of this.
I am not affected myself (Ubuntu 20.04), the limit by default is 1000, which should be sufficient.
With some snaps mounted, I have 142 entries (mount|wc -l)
But is some cases, it seems that unionfs, onedrive or some other cloud system could induce high number of mount points.
mount without umount from a script? In a cron task?
See https://forum.vyos.io/t/large-numbers-of-unionfs-fuse-mountpoints/1032
and https://lei.im/too-many-fuse-filesystems-mounted/
@krillin666: It would be useful not only to count but also to list the duplicates in mount to find the origin of the issue

[probonopd]

I'd like to find out what causes so many FUSE mounts to be there.

[BobSynfig]

I think this is connected to Flatpak, @krillin666 didn't mention this flatpak/flatpak#4051
There are some (known) bugs in Flatpak leading to this: flatpak/flatpak#5104
Also here https://ask.fedoraproject.org/t/flatpak-installation-and-update-errors/15245
Is the user member of fuse group?
Is it because of mix of install of Flatpak with sudo and unpriviledged user?
Some more info about revokefs could be found here https://www.altlinux.org/Flatpak and here https://www.altlinux.org/Control (use Google Translate, I don't understand russian either)

Once again, AppImageKit is not the root cause of this, just a "victim" of the lack of available mountpoints in the system in Fedora because of Flatpak!

P.S.: Try to change sockets authorizations for Flatpak's sockets with Flatseal, there are options for X11 and Wayland.

[hyuri]

Same issue here.

@probonopd

When this happens, what is the output of mount, do you see many fuse mounted mountpoints there?

My output of mount is 1035 lines. The last 1000 lines are all appimagelauncher-lite.AppImage similar to this:

appimagelauncher-lite.AppImage on /tmp/.mount_appimayJ2D6d type fuse.appimagelauncher-lite.AppImage (ro,nosuid,nodev,relatime,user_id=1000,group_id=1000)

Seems like this issue:
TheAssassin/AppImageLauncher#213

[hyuri]

For those affected like me:

I managed to temporarily alleviate the problem by unmounting all of the AppImage fuses running this command:
mount -l | grep ".mount_appima" | awk -F " " '{print "fusermount -u " $3}' | bash

⚠️ You should probably close any AppImages you might have running before running the command.