I installed a packaged postfix on a server and it installed OpenSSL-1.0.1e along with it. OpenSSL-1.0.1e doesn't have RSA capabilities, so I installed OpenSSL-1.0.1g. I thought that the old openssl would be replaced, but the server now has both of them. When I do an 'openssl version', it shows OpenSSL-1.0.1e. Is there some file in Linux that determines what the dominant program is supposed to be? I have a program that needs to find OpenSSL-1.0.1g to perform RSA operations. There is no way that the program can be selective within itself.

$PATH
But that's not what you really want to know.
$something > /path/to/binary_version_you_want

That might work
Or you could just uninstall version 1e

Thanks. I am afraid that the program using 1e might not function if it is uninstalled. I am going to experiment with installing 1g or h before installing postfix and see if postfix uses it or installs 1e anyway.

Try it and see.
I have a feeling you'll be pleasantly surprised and if not, you can re-install it.
Just make sure you've downloaded everything you need for the rollback before you do, just in case.

Can't take a chance on it. If this program stops working, people around the world are going to be upset. I have found that thing seem to be running ok without 0.1g being the predominate program. Apparently the other program is finding 0.1g itself and generating the RSA key correctly.

Just a suggestion, but the first thing I do when I get somewhere is build a test environment. I'd think the sheer terror of making changes on live servers without being absolutely certain of the result I'm about to get would send me to an early grave.

Yes, good advice. A fellow once asked me how I seemed to keep out of trouble with management, while everyone else, including himself, got chewed out for mistakes from time to time. I told him that one's goal in any company should always be to continuously cover your a%# from every possible problem that might come up, to keep yourself out of trouble.