What is the technical differences between "update" and "upgrade" with yum?

I frequently use the following when updating/upgrading RPM-based distros (CentOS, RHEL, and Fedora in my case):

yum -y update && yum -y upgrade

However, I'm not sure exactly how the two yum commands differ.

What are the advantages of update over upgrade, and vice versa?

1 Answer

According to man yum:

update:

If run without any packages, update will update every currently installed package. If one or more packages or package globs are specified, Yum will only update the listed packages. While updating packages, yum will ensure that all dependencies are satisfied. […]

If […] the --obsoletes flag is present yum will include package obsoletes in its calculations - this makes it better for distro-version changes, for example: upgrading from somelinux 8.0 to somelinux 9.

upgrade:

Is the same as the update command with the --obsoletes flag set.