YUM (Yellowdog Updater, Modified)

YUM (Yellowdog Updater, Modified) is a command-line package management utility for RPM-based Linux distributions such as Red Hat Enterprise Linux (RHEL), CentOS, and Rocky Linux. It automates installing, upgrading, and removing software, and it automatically resolves the dependencies between packages so that everything a program needs is installed together. YUM originated with the Yellow Dog Linux distribution and became the standard package manager across the Enterprise Linux family before being succeeded by DNF.

What is YUM?

YUM sits on top of the low-level RPM package format. RPM installs and tracks individual packages, but on its own it does not automatically fetch dependencies or coordinate updates. YUM adds that intelligence: given a request to install a package, it consults software repositories, works out the full set of dependencies, downloads everything required, and installs it in the correct order. This turns what could be a tedious, error-prone manual process into a single command.

First released in 2003 as an open-source project, YUM was created to improve on earlier package tools and to give system administrators a reliable way to manage software across many machines. It became the default package manager for CentOS, RHEL, and other RHEL forks for well over a decade.

How YUM works

YUM uses a client, repository model. Repositories store packages along with metadata describing each package's version, contents, and dependencies. When a user requests an operation, YUM:

• Contacts the configured repositories and downloads their metadata.
• Calculates the full dependency tree for the requested package.
• Downloads the needed packages and their dependencies.
• Installs or upgrades them as a single transaction that can be recorded and, if necessary, rolled back.

Multiple repositories can be configured at once, for example, the base distribution repositories plus community repositories such as EPEL, giving access to a wide range of software from one tool.

Why YUM matters

Consistent, automated package management is fundamental to operating Enterprise Linux at scale. In HPC clusters and enterprise fleets, administrators need to install identical software and apply security patches across hundreds or thousands of systems reliably. YUM's dependency resolution, transaction history, and repository support make those operations repeatable and auditable, which is why it became a cornerstone of the Enterprise Linux toolchain.

YUM and DNF

Modern Enterprise Linux releases, including current versions of Rocky Linux, ship DNF (Dandified YUM) as the default package manager. DNF is a rewritten successor with a faster and more robust dependency solver and a cleaner API, but it deliberately preserves YUM's command syntax and behavior. On these systems the yum command typically still works as an alias for dnf, so existing scripts and administrator habits carry forward. CIQ provides commercial support for Rocky Linux, including its package management and update tooling.