Update & Upgrade Policies

Unpatched packages are one of the most common ways systems get compromised — publicly known vulnerabilities in outdated software give attackers a reliable, low-effort way in. Keeping the OS and installed packages current closes off that path.

Debian-based distributions (e.g. Ubuntu)

apt update   # download package information from the configured sources
apt upgrade  # install available upgrades for all packages from the configured sources

RHEL / Fedora-based distributions

dnf update   # newer releases (Red Hat Enterprise Linux 8 and later)
yum update   # older releases (Red Hat Enterprise Linux 7 and earlier)

Tip

update refreshes the package index; upgrade actually installs the newer packages. Running update alone will not patch anything — both steps are required.