I've recently installed AIJ on a number of systems running Ubuntu-20.04 LTS, and discovered a fairly recent issue which could affect others running distributions derived from Debian. The underlying problem is that a shared object library, "libawt_xawt.so" has been moved from package openjdk-11-jre-headless to openjdk-11-jre, however package lists and dependencies have not been correctly updated. There is a bug report
here. Up until the library was moved, it was only necessary to install openjdk-11-jre-headless in order to run AIJ on Debian-derived systems. It is currently necessary to install openjdk-11-jre as well.
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Michael Collins
Instrumentation Group
Lowell Observatory
Flagstaff, Arizona