On the first run, eagle needs write access to the directory
%%PREFIX%%/share/eagle5/bin
in order to write a program key file. This can be done by executing
eagle as root or temporarily allowing a normal user to write this
directory (by suitable chown'ing).

Eagle usually creates an "eagle" directory in the user's home
directory upon initial startup. If this user does no longer want to
work on projects with eagle (e.g. the root account has been used to
create the mentioned key file), this directory can safely be deleted.