This describes how to set up ssl certificates to enable encrypted connections from PgAdmin on some client machine to postgresql on a server machine. The assumption is that postgresql (compiled with ssl support) and openssl are already installed and functional on the server (Linux). PgAdmin is already installed on the client (either Windows or Linux).
On the server, three certificates are required in the data directory. CentOS default is /var/lib/pgsql/data/: 
root.crt (trusted root certificate)
server.crt (server certificate)
server.key (private key)

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