Merge pull request #9482 from Icinga/9477-2.13

Docs: Add RHEL 9 installation instructions

CHANGELOG.md

@@ -10,7 +10,7 @@ Released closed milestones can be found on [GitHub](https://github.com/Icinga/ic
 ## 2.13.5 (2022-08-11)
 
 Version 2.13.5 is a maintenance release that fixes some bugs,
-improves logging and updates a bundled library.
+improves logging and updates the documentation as well as a bundled library.
 
 ### Bugfixes
 
@@ -20,6 +20,8 @@ improves logging and updates a bundled library.
 * Icinga DB: Add missing Redis SELinux policy. #9473
 * Windows: Don't spam the event log with non-error startup messages. #9457
 * Windows: Update bundled version of OpenSSL. #9460
+* Docs: Update RHEL 8 installation instructions. #9482
+* Docs: Add RHEL 9 installation instructions. #9482
 
 ## 2.13.4 (2022-06-30)
 

doc/02-installation.md

@@ -122,18 +122,18 @@ rpm --import https://packages.icinga.com/icinga.key
 wget https://packages.icinga.com/subscription/rhel/ICINGA-release.repo -O /etc/yum.repos.d/ICINGA-release.repo
 ```
 
-If you are using RHEL you need to additionally enable the `optional` and `codeready-builder`
+If you are using RHEL you need to additionally enable the `codeready-builder`
 repository before installing the [EPEL rpm package](https://fedoraproject.org/wiki/EPEL#How_can_I_use_these_extra_packages.3F).
 
-#### RHEL 8
+#### RHEL 8 or Later
 
 ```bash
-ARCH=$( /bin/arch )
+ARCH=$(/bin/arch)
+OSVER=$(. /etc/os-release; echo "${VERSION_ID%%.*}")
 
-subscription-manager repos --enable rhel-8-server-optional-rpms
-subscription-manager repos --enable "codeready-builder-for-rhel-8-${ARCH}-rpms"
+subscription-manager repos --enable "codeready-builder-for-rhel-${OSVER}-${ARCH}-rpms"
 
-dnf install https://dl.fedoraproject.org/pub/epel/epel-release-latest-8.noarch.rpm
+dnf install https://dl.fedoraproject.org/pub/epel/epel-release-latest-${OSVER}.noarch.rpm
 ```
 
 #### RHEL 7
@@ -267,7 +267,7 @@ systemctl start icinga2
 <!-- {% endif %} -->
 
 <!-- {% if rhel %} -->
-#### RHEL 8
+#### RHEL 8 or Later
 
 ```bash
 dnf install icinga2
@@ -380,7 +380,7 @@ yum install nagios-plugins-all
 <!-- {% endif %} -->
 The packages for RHEL depend on other packages which are distributed as part of the EPEL repository.
 
-#### RHEL 8
+#### RHEL 8 or Later
 
 ```bash
 dnf install nagios-plugins-all