Adding third-party repos: EPEL, CRB and Remi on Rocky 9 (tested)

When to use it

The system repos do not carry what you need (htop, glibc-static, a newer PHP), so you add a third-party source. Order matters: EPEL first, Remi depends on EPEL; CRB is not third-party at all — it ships with Rocky but is disabled by default.

Order: EPEL → CRB → Remi

1. EPEL: dnf install epel-release; the package comes from extras, and enables epel plus epel-cisco-openh264;
2. CRB: disabled by default; enable per command with --enablerepo=crb instead of permanently;
3. Remi: install EPEL first, then remi-release, which enables remi-safe and remi-modular.

EPEL: two more repos after install

sudo dnf install -y epel-release
dnf repolist --enabled

repo id              repo name
appstream            Rocky Linux 9 - AppStream
baseos               Rocky Linux 9 - BaseOS
epel                 Extra Packages for Enterprise Linux 9 - aarch64
epel-cisco-openh264  Extra Packages for Enterprise Linux 9 openh264 (From Cisco) - aarch64
extras               Rocky Linux 9 - Extras

Packages from EPEL become available immediately, for example:

dnf list available htop

htop.aarch64    3.3.0-1.el9    epel

CRB: off by default, enabled per command

sudo dnf install -y glibc-static
sudo dnf install -y --enablerepo=crb glibc-static
rpm -q glibc-static

Error: Unable to find a match: glibc-static          ← CRB not enabled
...
glibc-static-2.34-283.el9_8.aarch64                  ← only with CRB

CRB (CodeReady Builder) carries development and build dependencies (*-devel, glibc-static and similar). No need to turn it off afterwards — --enablerepo applies to that single command.

Remi: EPEL first, then the release package

sudo dnf install -y https://rpms.remirepo.net/enterprise/remi-release-9.rpm
dnf repolist --enabled | grep -i remi

remi-modular    Remi's Modular repository for Enterprise Linux 9 - aarch64
remi-safe       Safe Remi's RPM repository for Enterprise Linux 9 - aarch64

Remi provides newer PHP/Redis and similar. PHP versions are selected through module streams (remi-modular); run dnf module list php before installing.

Conflict matrix: one package, several sources

Package	Possible source	Advice
htop, tmux and friends	epel	Use directly; conflicts are rare
glibc-static, *-devel	crb	Enable with --enablerepo=crb per command
php, redis	remi-modular / system modules	Check dnf module list and use one source only
nginx	appstream / nginx official repo	Pick one; do not mix

There is one rule: let exactly one source provide a given package. If a version changes after --enablerepo, or dnf update wants to replace a system package with a third-party build, two sources are fighting over it.

Common traps

• Permanently enabling a third-party repo: an enabled=1 third-party repo takes part in dnf update and may replace system packages; prefer --enablerepo;
• Installing Remi without EPEL: remi-release dependency resolution fails or leaves a half-configured repo;
• GPG key not imported: the first install asks for confirmation, which hangs scripts; think before reaching for --nogpgcheck.

Practice: enable CRB for one package only

Prerequisite: Rocky 9 with root or sudo.

sudo dnf install -y glibc-static            # expected to fail
sudo dnf install -y --enablerepo=crb glibc-static
rpm -q glibc-static
dnf repolist --enabled | grep -c crb        # expected 0: CRB not enabled permanently

Checks:

1. The first command reports Unable to find a match
2. The second succeeds and rpm -q prints a version
3. The third prints 0, proving --enablerepo did not change permanent configuration

Next steps

• The three ways to resolve repo conflicts: Repository conflicts
• Building a local repo: Offline package installs
• Package history and rollback: dnf history undo