On Wed, 4 Jan 2017, Locane wrote:
My questions are, who decides what packages are current for CentOS when I "yum upgrade"?
That's determined by the repositories defined and enabled in /etc/yum.conf and /etc/yum.repos.d/*.repo. To see the repositories enabled by your system, ask yum:
yum repolist
Each repository maintains a different set of packages. For any given package, order is determined by
epoch > version > release
To see those values for the packages installed on your system:
rpm -qa --qf '%{name}\t\t%{epoch}\t%{version}\t%{release}\n' | sort
Epoch is essentially a hack that can override a change in a package's version numbering. Most packages don't have an epoch number, but check out the epochs on bind-libs and (32!) and dhclient (12).
So for each package name, the package with the highest epoch:version:release is "current." That allows a package in the updates repository to be installed over one currently installed on your system.