[FR]: Package the AppImage with the uruntime

[Samueru-sama]

Description

The uruntime doesn't need FUSE at all to mount the AppImage and has a ton of other useful features.

Who's implementing?

• I'm willing to implement this feature myself

The problem

The uruntime offers the following advantages over the type2-runtime:

• Can use namespaces to mount instead of FUSE, and if that is not possible either it falls back to self extract to /tmp and run, so the appimage will always run no matter if FUSE is not present on the system at all.

• The uruntime can be configured to keep the mountpoint, that means launches are instant. This feature is not enabled by default, to enable it an embedded string in the runtime needs to be edited before running appimagetool: sed -i 's|URUNTIME_MOUNT=[0-9]|URUNTIME_MOUNT=0|' /path/uruntime

• Supports additional flags like --appimage-portable-share and --appimage-portable-cache.

• User can set additional env variables by making a $0.env file next to the appimage.

Possible solutions

https://github.com/VHSgunzo/uruntime

In order to use all you need to do is download the uruntime-appimage-squashfs-lite-$ARCH artifact and pass it to appimagetool using the --runtime-file flag.

Additional context

The uruntime also supports DWARFS, which is better than squashfs in every single way (smaller and faster launch times) however this will introduce a breaking change if you switch to the dwarfs version, most notably it will stop working with appimagelauncher. (it will keep working with AM and Gearlever though). Also in this case you cannot use appimagetool and would need to use the uruntime itself, which yeah it can also pack itself without appimagetool.

[dumbmoron]

• Can use namespaces to mount instead of FUSE, and if that is not possible either it falls back to self extract to /tmp and run, so the appimage will always run no matter if FUSE is not present on the system at all.

This might be problematic on Ubuntu, where we need to unpack the AppImage first to be able to add an AppArmor rule so that the Chromium sandbox can use user namespaces. Does it fall back to fusermount if user namespaces are unavailable?

Other than that, sounds very promising to me.

[Samueru-sama]

Does it fall back to fusermount if user namespaces are unavailable?

Yes, by default it tries to use FUSE first, if that fails it uses namespaces and if that fails it will extract to TMPDIR and run.