Extracting AppImages

All recent type 2 AppImages (created with an appimagetool newer than Nov 15 2017, commit #51fdac2) can be run with extra parameters, all with a naming pattern "*--appimage-<something>".

--appimage-help

You can list them all by running it with --appimage-help:

./WhatEver-x86_64.AppImage --appimage-help
AppImage options:

--appimage-extract              Extract content from embedded filesystem image
--appimage-help                 Print this help
--appimage-mount                Mount embedded filesystem image and
                                print mount point, then wait for kill with Ctrl-C
--appimage-offset               Print byte offset to start of
                                embedded filesystem image
--appimage-signature            Print digital signature embedded in AppImage
--appimage-updateinfo[rmation]  Print update info embedded in AppImage
--appimage-version              Print version of AppImageKit

--appimage-extract

If you run ./WhatEver-x86_64.AppImage --appimage-extract, the AppImage will auto-extract its contents into AppDir (currently as a sub-directory squashfs-root in the current location. Then just change into that directory to look around and see what elements the AppImage is composed from. Advanced users or developers may even use that feature to "repair" a buggy AppImage by swapping library versions or icons, .desktop files and AppRun scripts in the extracted AppDir hierarchy, test them in-place and finally repackage the AppDir again with the help of appimagetool.

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^{(This is an ongoing development. More options may appear of the coming period. Check your newest AppImages to see what got added.)}