You just need to do apt-get install --only-upgrade <packagename>
. This will upgrade only that single package, and only if it is installed.
If you wish to install the package if it doesn't exist, or upgrade it if it does, you may leave out --only-upgrade
.
The goal of fpm is to make it easy and quick to build packages such as rpms, debs, OSX packages, etc.
fpm, as a project, exists to help you build packages, therefore:
Postfix is the default Mail Transfer Agent (MTA) for Ubuntu. It is in Ubuntu's main repository, which means that it receives security updates. This guide explains how to install and configure postfix and set it up as an SMTP server using a secure connection.