If, when running Fade In from the command line on Linux, the application fails to start and you receive an error like:
fadein: error while loading shared libraries: <libraryname>.so.1: cannot open shared object file: No such file or directory
that is an indication that you may have installed the 32-bit version of Fade In on a 64-bit version of Linux, or vice versa.
Please double-check that you've downloaded the correct version of Fade In for your architecture.
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You might also check if your repository has updated to a more recent version of a particular library. If so, you may be able to download the required version of the library in question and install it alongside the current newer version.
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One more thing you can try is compiling the missing library from source. For this, you'll need to download the source code (generally as a .tar.gz archive, and preferably from the official project site). Then, unarchive it into its own folder.
The steps for compiling and installing are the similar between libraries. Usually a file called INSTALL or something similar will give specific instructions, but generally speaking it involves basically typing:
sudo make install
inside the directory where you unarchived the source tarball.